Interventions on Traffic lights

Traffic Signals: Complete Guide, Standards, Stakeholders and Maintenance

The traffic lights, also known as traffic signal lights or tricolor signal lights, are these luminous devices that regulate traffic at intersections by alternating green, yellow, and red. More than just a trio of lamps, a traffic light is a safety equipment controlled by a controller, subject to strict standards, and any minor failure creates an immediate danger. In this guide, we cover everything: operation and types, technical vocabulary, regulations and standards, main players and manufacturers, criteria for choosing a maintenance provider, and how an application like KARTES streamlines the tracking of interventions on a network of traffic lights. A technical subject at the intersection of road safety, accessibility, and the manager's liability.

A reference point to understand the issue. The first French traffic light was installed in Paris in 1923, and since then, these devices have multiplied in all urban areas. Nevertheless, more than 10,000 accidents occur each year at intersections equipped with traffic lights, proving that the traffic light does not eliminate the need for vigilance or impeccable maintenance. Behind each traffic light lies a controller, LED heads, sound repeaters, and an absolute requirement: that it functions without failure. A failed traffic light at an intersection threatens an accident. Hence, the vital importance of maintenance.

Presentation of traffic lights: everything you need to know

Let's start with the basics. In industry terminology, we refer to tricolor traffic lights, or SLT, and signalized intersections. The traffic light never acts alone: it is part of a system controlled by a controller, which coordinates the phases to manage the flow of vehicles and pedestrians. This system, which is standardized and certified, is one of the most technically advanced pieces of equipment in road infrastructure.

What is a traffic light?

A traffic signal is a luminous device designed to regulate traffic, allowing or prohibiting passage through standardized colors. Green to go, yellow to slow down and stop, red to stop: this universal language organizes traffic at intersections. Its primary purpose: to separate in time incompatible user flows, to avoid conflicts and accidents.

Ask yourself: why traffic lights rather than a simple stop? Because on a high-traffic road, traffic lights allow for the management of dense and fast-moving traffic flows, the organization of complex priorities, and the securing of pedestrian crossings. By forcing some to stop, they allow others to cross the intersection safely. The traffic light is the premier regulation tool for busy intersections, particularly in urban areas.

What is a traffic light intersection?

A traffic light intersection is an intersection where traffic is controlled by signal lights operated by a controller. This controller, the real brain of the intersection, orchestrates the phases: it decides when each light turns green, yellow, or red, according to a program or by adapting to traffic. Without it, the lights would just be an assembly of lamps without logic.

Conflict management over time is the fundamental principle. The controller separates incompatible movements, alternatively granting passage to different streams. However, even a sophisticated traffic signal works well only if the geometric layout of the intersection is appropriate. Design and operation go hand in hand. A poorly designed intersection, even if well equipped, will function poorly. It is an entire art, combining geometry, programming, and equipment.

What are the different types of traffic signals?

Where the family expands, and that's enlightening. The regulation defines several types of light signals, identified by codes, each with a specific role. Knowing these types is understanding the logic of a traffic light intersection.

Type of fire	Recipient	Particularity
Tricolor traffic light R11	Vehicles at an intersection	Green, yellow, red, generally circular
Pedestrian crossing R12	Pedestrians	Green or red silhouette
Audible pedestrian crossing R25	Pedestrians, including the blind and visually impaired	Mandatory sound repeater
Directional beacon R19	Vehicles according to a direction	Arrow pictogram
Public transport fire	Buses and trams	White lights, bar and disc
Bicycle light	Cyclists	Bicycle pictogram, possible give-way

The R11 traffic light is the most common, the one that controls vehicles at intersections, with its green light at the bottom. The R12 pedestrian traffic light, with a silhouette, manages crossings. The R25 traffic light, equipped with a sound repeater, is essential for blind or visually impaired people. The directional traffic lights with arrows manage specific movements. And the white traffic lights, with a bar and disc, are reserved for public transport. Each type meets a specific need for regulation.

What do the colors of traffic lights mean?

The color code is universal, but its subtleties deserve a reminder. The green allows passage. The yellow signals the transition to red and requires stopping if it can be done safely. The red mandates a complete stop. This sequence, green, yellow, red, structures the rhythm of the intersection.

Some signals have particular behaviors. The flashing yellow light indicates an intersection where the signals are out of service or in degraded mode, inviting caution and respect for normal priorities. Public transport signals, which are white, feature bars and a disc, with a specific code. The red Greek cross, sometimes visible at the back of a signal, repeats the red for vehicles coming from behind, but remains optional. A rich language, codified in every detail.

How does a traffic light work?

The system relies on several coordinated components. The light head, now most often LED-based, emits the colored light. The controller, or traffic signal controller, manages the phases according to a program. The electrical power supply and wiring connect all components. And the repeaters, which may be auditory or tactile, complete the device to ensure accessibility.

Switching to LED has transformed these equipment. More energy-efficient, more durable, and more visible than the old bulbs, LED heads have largely replaced the old technology. The controller, on the other hand, manages precise times: duration of green, yellow, red, clearance time to free the intersection. Some controllers adapt to real-time traffic, via sensors or loops in the road. The traffic light is thus a sophisticated electronic system, far from being just a simple lamp.

The technical vocabulary of traffic signals

A small survival glossary, to decode a specification document or a conversation with a maintainer. This jargon keeps coming up constantly in the field of lighting signage.

• SLT : tricolor light signaling, the generic term in the profession.
• Signalized intersection : intersection controlled by traffic lights operated by a controller.
• Controller : automaton managing the phases of the intersection.
• Headlight : luminous element, today most often LED.
• R11 : traffic light for vehicles at an intersection.
• R12 and R25 : pedestrian signals, the R25 being equipped with a sound repeater.
• Sound Repeater : accessibility device for the blind and visually impaired.
• Phase : period during which a set of movements is authorized.
• Clearance Time : time allowed to clear the intersection before the next traffic flow.
• Greek cross : optional repetition of red at the back of the light.

Regulations and Standards for Traffic Signals

Set aside the regulatory framework, and it is dense, because it concerns safety at intersections. Traffic signals cross several texts: interministerial instructions, performance decrees, product standards, accessibility and maintenance rules. Understanding this stack is key to avoiding non-compliance, which exposes to sanctions and engages the manager's liability. Let's unravel the thread, from the reference text to technical standards.

What is the reference text for traffic signals?

Everything starts with the Interministerial Instruction on Road Signaling, and more specifically with its 6th part, dedicated to permanent traffic lights. This text defines the scope of application, the conditions for use, and the characteristics of each light signal. It complements the decree of November 24, 1967, on road signaling. Every traffic light installed on public roads must comply with it.

This 6th part also sets crucial timing rules. The minimum green time is 6 seconds, although 10 seconds are preferable. Clearance times allow a vehicle or pedestrian to clear the conflict zone, calculated based on a reference speed. And the maximum waiting time for a road user must not exceed 120 seconds. These rules ensure a safe and credible operation, a condition for road users' compliance with traffic signals.

What standards govern fire heads?

The reference standard for traffic lights is the NF EN 12368. It specifies the optical characteristics of circular signals with a diameter of 200 or 300 millimeters, their resistance to environmental conditions, and the CE marking requirements. Since February 1, 2009, all circular signals of these diameters must bear the CE marking under this standard.

Several texts frame the certification and performance requirements. The decree of July 26, 2012 sets the required performance levels and the rules for commissioning permanent tricolor traffic lights, referring to the classes of the NF EN 12368 standard: luminous intensity, chromaticity, ghost effect, durability. The ASCQUER is the notified body appointed by France for CE certification of these signals. The NF P99-200 standard complements the whole by addressing pictogram traffic lights. A demanding technical framework for a safety equipment.

What rules for fire controllers?

The controller, the brain of the intersection, is also strictly regulated. Any permanent traffic light controller used on public roads must comply with the requirements set forth in the decree of June 18, 2003, concerning the conformity certificate for permanent traffic light controllers. This certificate guarantees the reliability of the equipment that controls the entire intersection.

The NF EN 12675 standard governs the functional safety of signal controllers. It serves as a sort of dictionary of faults that a controller must be able to identify. A decree sets, for France, the list of faults that must be monitored. The stakes are crucial: a failing controller could, for example, display green simultaneously on two conflicting traffic streams, a catastrophic scenario. Therefore, the functional safety of the controller is an absolute requirement, strictly regulated.

What accessibility rules apply to pedestrian signals?

Accessibility is a strong obligation, at the heart of recent regulations. The law of February 11, 2005 requires that pedestrian traffic lights be accessible to blind and visually impaired people. Specifically, the R25 traffic lights must be equipped with audio repeaters, made mandatory by the decree of April 2, 2012 amending the 1967 decree. These devices vocally announce the phase of the traffic light to visually impaired pedestrians.

Requirements have become more specific over time. The decree of September 23, 2015, promoting active mobility, requires that sound messages also indicate the location, that is, the name of the crossed street. The NF S32-002 standard specifies the technical characteristics of these repeaters. Key point: the regulation does not only require equipping the signals, but also maintaining these repeaters in good working condition. A silent repeater is a non-compliance, and an exclusion for visually impaired pedestrians. Therefore, maintaining accessibility is a full-fledged obligation.

What standards for electrical installations?

A traffic light intersection is an electrical installation subject to safety standards. The NF EN 50556 standard governs the electrical installations of traffic light intersections. The NFC 17-200 standard regulates outdoor lighting installations, which often include these equipment. The protection rating, defined by the NF EN 60529 standard, ensures the resistance to water and dust of the enclosures.

Electrical safety is essential, both for users and for personnel involved. Work on lighting signage must strictly comply with regulatory requirements, and the personnel involved must be authorized. Junction boxes meet specific requirements, sometimes with a prohibition on metal boxes for safety reasons. This electrical aspect makes traffic light maintenance a task for authorized specialists. You don't tinker with a traffic light intersection.

Which standard governs the maintenance of traffic lights?

Here is the key standard for our subject: the NF P99-050, revised in March 2018, which deals with the maintenance principles of traffic signal intersections. It defines maintenance actions and their periodicity, lists the various levels of service status, and specifies response times. It is the structuring reference for any traffic signal manager.

His contribution is considerable. NF P99-050 provides the manager with keys to draft a precise specification, anticipating essential maintenance operations from the design phase of the intersection. It distinguishes between preventive and corrective maintenance, sets intervention deadlines according to severity, and structures the follow-up. Relying on this standard means rigorously organizing the maintenance of your fleet. Anticipating maintenance from the design phase, as the standard recommends, avoids many future problems. It is an essential text.

Who is responsible for traffic lights?

The responsibility lies with the road manager, most often the municipality or the metropolitan area. As the owner and operator of the intersection, it must ensure the proper functioning and compliance of its traffic lights. This responsibility stems from the traffic enforcement authority and the general obligation of safety.

This responsibility is heavy, as a failing fire system creates an immediate danger. A failed fire alarm, a faulty controller, a silent sound repeater can engage the manager's liability in case of an accident or complaint. Being able to demonstrate maintenance in accordance with NF P99-050, regular and documented, therefore constitutes an essential protection. The traceability of maintenance is not just a good practice: it is a legal and safety necessity. We will come back to this when discussing tracking tools.

Key actors and service providers for traffic signals: the top 10

Who designs, manufactures, installs, and maintains traffic signals in France? The sector involves several families of stakeholders: manufacturers of luminous signaling, maintainers specialized in the field, accessibility specialists, and certification and reference organizations. Here is an overview of recognized stakeholders, without a fixed hierarchy, since the right interlocutor depends on the need and the network.

Who manufactures traffic signals?

The manufacturing of tricolor traffic signal equipment is a specialized market, with producers making certified traffic light heads, controllers, and automation systems. These manufacturers master optics, electronics, and compliance with standards.

1. Lacroix, with its lighting signage activity, a major player in the sector in France.
2. SEA Signalisation, recognized manufacturer of traffic lights and pedestrian boxes.
3. Fareco, specialist in lighting equipment and repeaters.
4. Aximum, a signaling actor, including its tricolor lighting signage.

Who maintains the traffic lights?

The maintenance of the lights is entrusted to specialized companies in lighting signage and electrical engineering, or carried out by the technical services of large municipalities. These actors intervene on the heads, controllers, and installations.

5. Specialized subsidiaries of major energy groups, which operate and maintain traffic lights.
6. Lighting signage maintenance companies, present on the road infrastructure markets.
7. Metropolitan technical services, which often manage their fleet in-house or by overseeing service providers.

Who equips the lights for accessibility?

The accessibility of pedestrian crossings has led to the emergence of specialists in audible repeaters and devices for visually impaired individuals. These professionals provide and maintain these mandatory equipment.

8. Experts in sound and accessibility fires, including well-known industry actors.
9. Manufacturers incorporating repeaters into their pedestrian light ranges.

Which organizations oversee the sector?

Several institutions hold authority. The CEREMA is the technical reference for traffic lights intersections, with its guides and documents. The ASCQUER ensures equipment certification. The AFNOR publishes standards, such as NF EN 12368 or NF P99-050. And the SER, the association of road equipment manufacturers, represents the industry.

10. CEREMA, ASCQUER, AFNOR and SER, reference organizations for certification, standardization and technical recommendations.

This overview reveals a highly technical sector with strong requirements for compliance and safety. For a manager, this diversity means a chain of actors to coordinate, from certified procurement to maintenance in accordance with NF P99-050. And it is precisely over time, through maintenance, that the safety of a traffic light intersection is determined. Installation alone is not enough; it is also essential to maintain operational equipment at all times, otherwise a danger may be created.

How to choose a maintenance provider for traffic signals?

Selecting the right maintenance provider is a critical decision, as a failed fire alarm creates an immediate danger. A community or a metropolitan area does not choose a traffic signal maintainer at random: it concerns the safety at intersections and their own liability. Step-by-step method.

Which technical criteria should be checked first?

First requirement: advanced technical expertise. A traffic light intersection involves electronics, LED heads, a complex controller, repeaters, and electrical installations. The service provider must be proficient in these equipment, know how to diagnose a controller, troubleshoot a head, check an audio repeater, and work safely on electrical systems. Ask to see a sample intervention report: its accuracy speaks volumes about the company's seriousness.

• Competence in lighting signaling : heads, controllers, automatons.
• Electrical Authorization : intervention in safety on the installations.
• Compliance with NF P99-050 : structured maintenance, periodicity, deadlines.
• Mastery of accessibility : control of sound repeaters.
• Responsiveness : response time to a faulty fire alarm, a vital criterion.
• Traceability : geolocated reports, photos, intersection history.

Why is responsiveness vital?

Here is the key point that distinguishes traffic signal maintenance: urgency. Unlike a damaged sign, a failed traffic light creates an immediate danger at the intersection. A turned-off light, a malfunctioning controller, and it's immediately a risk of accident, confusion, and danger for pedestrians and vehicles. Therefore, the response time is an absolutely vital criterion, much more so than for other equipment.

The NF P99-050 standard sets intervention deadlines according to the severity of the breakdown. A serious service provider commits to these deadlines, has on-call staff and spare parts, and intervenes quickly. On site, the ability to repair an intersection in an emergency, day and night, including weekends, makes all the difference. A maintainer unable to guarantee this responsiveness exposes the manager to a persistent danger. Choosing an organized service provider for emergencies is crucial.

What questions to ask before signing?

A few concrete questions, to bring up in the selection meeting. They quickly separate the serious candidates from the opportunists.

1. What is your guaranteed response time for a faulty fire alarm, day and night?
2. Do you have an on-call service for critical breakdowns?
3. Is your maintenance in compliance with the NF P99-050 standard?
4. How do you ensure the proper functioning of the sound repeaters?
5. Are your intervention reports geolocated, timestamped, and photographed?
6. Can I view the history and service status of each intersection?

What warning signals should cause retreat?

Skepticism toward a provider vague about response times, unable to produce a standard report, or offering abnormally low pricing. On equipment where failure creates an immediate danger, low cost can cost lives. Another red flag: the absence of digital traceability. A company that intervenes on an ad-hoc basis, without exploitable data or an overall view of the fleet, leaves you blind to the actual condition of your intersections and your compliance with NF P99-050.

The best-organized managers now impose a standard of geolocated digital reporting. Every intersection controlled, every incident handled is recorded, photographed, and plotted on a map, along with the service status and compliance verdict. This level of requirement changes the game, especially for a network of tens or hundreds of scattered intersections. And that's exactly where an intervention management application comes into play.

Comment KARTES improve traffic signal maintenance?

We have discussed operations, standards, and service providers. What remains is the question that occupies managers on a daily basis: how to pilot a network of traffic lights, with their heads, controllers, and repeaters scattered throughout an entire urban area, while ensuring uninterrupted availability? This is precisely the field of KARTES, a mobile application for managing and tracking field interventions, perfectly suited for the maintenance of lighting signage.

What is KARTES concretely?

KARTES is a field intervention management solution. The principle: every traffic light intersection, every head, every repeater becomes a geolocated object on a map, with its own identifier, characteristics (type, controller, equipment, installation date) and its entire history. When an intervention occurs (head repair, controller diagnostic, repeater check, electrical inspection, preventive maintenance), it is recorded on a smartphone, timestamped, photographed, and linked to the relevant equipment. The park's memory is built automatically.

Where a manager juggled yesterday between scattered plans, files, and emergency reports, KARTES centralizes on an interactive map. This map becomes the live dashboard of the intersection park. And this data is worth its weight in gold to manage availability, prove maintenance in accordance with NF P99-050, and allocate budgets. On an equipment where a failure creates an immediate danger, this traceability takes on a particular dimension. Let's look at the contribution for each stakeholder.

From the community's perspective: controlled safety and responsibility

For a community or a metropolitan area, the benefit is summed up in three words: availability, compliance, controlled responsibility. One can see, on a single map, the status of the network: which intersections are working, which are out of service, and which are waiting for a preventive intervention. Availability, vital here, becomes measurable rather than expected.

The dimension of responsibility is crucial here. We are dealing with equipment whose failure creates an immediate danger and may hold the manager liable in the event of an accident. Rigorous tracking of interventions, in accordance with NF P99-050, constitutes a decisive proof of due diligence. In the event of a dispute, the community that can demonstrate that it maintained and repaired its lights within the required timeframes is in a much stronger position. Traceability becomes a legal protection as well as a management tool, and in this area, it has no price.

Finally, budgetary arbitration. By aggregating data, the manager identifies the intersections that frequently break down, recognizes aging controllers, measures response times, and plans based on facts. Instead of endlessly repairing capricious equipment, a decision is made to replace it at the right time. Feedback shows that well-maintained data transforms a passive management into an informed control of the fleet.

From the maintainer's perspective: less paperwork, more fieldwork

For the technician maintaining the traffic lights, daily life changes radically. Before: noting the intervention on a form, taking a photo with his personal phone, re-entering the data at the office, trying to find out which intersection and which memory equipment. A tedious process, prone to forgetfulness and duplicates, especially painful when intersections are spread throughout the entire city.

With KARTES, the technician opens the application on site, selects the intersection on the map, logs the repair or inspection, takes photos directly in the app, and validates. Geolocation and timestamping are automatic. Double data entry disappears, and the report is ready. Every minute saved on administrative tasks becomes time gained on the field, precious for emergency interventions. And the viewable history prevents rediscovering a problem already addressed, or replacing a part recently changed.

• On-site entry : nature of the intervention recorded directly, without re-entry.
• Embedded Photos : condition of the head, controller, repeater, attached to the object.
• Automatic geolocation : no more unfindable intersections and equipment.
• Intersection History : the technician sees previous interventions.
• Reporting ready : maintenance evidence generated, documented compliance.

From the user's and resident's perspective: a safe and accessible intersection

And the user? They are the ultimate beneficiary. A faulty traffic light, a silent sound repeater, and that is a danger for both the driver and the pedestrian, especially the blind pedestrian deprived of their guidance. An effective intervention management system shortens the time needed to restore functionality, ensuring operational intersections. The safety of everyone directly depends on this availability.

For the resident, the issue is also that of daily safety and accessibility. A malfunctioning traffic light at a nearby intersection, or a broken sound repeater for a visually impaired neighbor, legitimately cause concern. In fact, residents often report these issues, and some local authorities incorporate these reports into their maintenance processes. A well-managed park, where faults are quickly identified and corrected, concretely reinforces the safety and inclusion of all. An operational and accessible intersection with traffic lights protects everyone, from drivers to visually impaired pedestrians.

In what KARTES does it reduce maintenance costs?

Cost reduction results from the addition of concrete gains. Let's recap the levers, because this is often the first question a decision-maker asks.

Lever	Effect on Costs
Elimination of double entry	Reduced administrative time, technicians focused back on the field
Geolocation of intersections	Optimized routes, accelerated emergency interventions
History by Equipment	Detection of problematic intersections, repair/replacement decision-making
Tracked preventive maintenance	Compliance with NF P99-050, evidence of due diligence
Reduction of downtime	Intersection available, danger avoided, safety preserved
Data-Driven Prioritization	Targeted investments on sensitive intersections

A telling example. Imagine a controller whose component gradually weakens without structured monitoring, leading to a complete failure of the intersection during peak hours. The danger is immediate, emergency intervention is costly, and the manager, without maintenance proof, sees their responsibility called into question. With preventive tracking in place, the defect is detected during an inspection, intervention occurs before the failure, and the danger is averted. KARTES makes visible what is deteriorating in silence. Turning scattered interventions into usable data, that is the real gain, and on the fires, this gain protects lives and responsibilities.

Let's be honest: no software can assist a controller or replace a head for the technician. KARTES does not replace professional expertise or the obligations of NF P99-050. The application is an organizational amplifier, not a magic wand. But when used properly, this amplifier changes the scale of what a team can manage, shifting maintenance from reactive and endured to proactive and controlled, which, on this critical asset base, changes everything.

Failures, lifespan, and reliability of traffic signals

A traffic signal appears robust, planted at the intersection for years. Yet its components wear out, become misaligned, and fail, sometimes at the worst moment. Knowing common failures helps anticipate rather than endure. An overview of the ailments that threaten heads, controllers, and repeaters.

What is the lifespan of a traffic light?

LED headlamps have a long lifespan, often exceeding ten years, much longer than the old incandescent bulbs. However, their brightness gradually declines, and their compliance must be monitored. The controller, a complex electronic component, also ages and may require replacement after several years. Sound repeaters, constantly in use, require regular monitoring. The limiting factor varies depending on the component, but regular maintenance remains the key to reliability everywhere.

What are the most frequent breakdowns?

The record of failures, observed on site, looks like this. The particularity here is that a breakdown often creates an immediate danger.

• Failing Burner Head : fire extinguished, LED out of service, immediate danger.
• Controller Failure : intersection in degraded mode or turned off.
• Silent audio repeater : compromised accessibility, non-compliance.
• Electrical failure : power supply interrupted, faulty wiring.
• Damaged mast : vehicle collision, corrosion, instability.
• Failure Detection : loops or sensors no longer detecting traffic.
• Vandalism : damaged, removed, tagged equipment.

The controller failure deserves attention, as its consequences can be serious. A failing controller can shut down the intersection, put it in flashing yellow, or, in the worst theoretical case, create a dangerous conflict. That is why controllers include safeguards that detect faults and switch to a safe mode. However, any controller failure remains critical and requires a rapid response. The reliability of the controller is the heart of the intersection's safety.

Why is preventive maintenance vital?

Corrective maintenance discovers failures at the worst possible moment, often when the intersection is already out of service and dangerous. Preventive maintenance, on the other hand, anticipates: inspection of heads, controller diagnostics, verification of repeaters, electrical checks. The NF P99-050 standard precisely structures this approach, defining the operations and their frequency. For a traffic light intersection park, a rigorous preventive approach is not optional: it conditions safety. An intervention management tool organizes and tracks this preventive maintenance, ensuring that no check is forgotten.

How to perform a diagnostic of a traffic light installation?

Before optimizing maintenance or proving compliance, it is first necessary to know the condition of your fleet. Many managers lack a clear vision of their intersections, accumulated over decades. The diagnostic corrects this blind spot. Here is a method applicable from small municipal networks to large metropolitan fleets.

Where to start the intersection inventory?

The starting point is the geolocated inventory. Every traffic light intersection is inventoried, its type, equipment, controller, condition, and level of compliance are noted. In the paper era, this work was lost in disparate folders. Today, it is directly entered on a digital map, each intersection becoming a localized and durable object. Without a reliable inventory, structured management and maintenance are impossible.

For a small network, the inventory is done quickly. For a large metropolitan park, the process is carried out by sectors, prioritizing the busiest and most sensitive intersections. The essential thing: a homogeneous grid, to ensure the evaluation is reproducible. This solid foundation conditions the entire maintenance strategy in accordance with NF P99-050 that will follow.

What points to check at each intersection?

An effective diagnosis covers several aspects, verified on site. The objective is a reliable picture of the actual condition and compliance of each intersection.

• Light Heads : operation, brightness, LED compliance.
• Controller : proper functioning, potential defects, age.
• Audio Repeaters : operation, messages, volume, compliance.
• Electrical installation : safety, wiring, enclosures.
• Supports and masts : condition, stability, corrosion.
• Detection : loops and traffic sensors.

How to leverage diagnostic data?

Once the data is collected, the real work begins: transforming it into an action plan. We distinguish between urgent issues (dangerous intersections, non-compliant repeaters) and programmable renewals. We plan for the replacement of aging controllers and accessibility compliance updates. The asset management strategy is directly fed by this diagnosis.

The value of a digital tool becomes evident here. The diagnostic map is not a static image: it lives, updates with each intervention, and keeps a history. It is precisely known when each intersection has been checked and with what result. This history, in line with the spirit of NF P99-050, constitutes a valuable proof of due diligence. The diagnostic stops being a forgotten report and becomes a permanent dashboard of the park's availability.

Common mistakes to avoid with traffic signals

Field experience leaves a rich collection of recurring errors. Knowing them is already avoiding them. Here are the most common ones, from design to daily management.

What design errors compromise an intersection?

Headline: Installing traffic lights without real justification. A poorly placed intersection with traffic lights creates unnecessary waiting times, encourages dangerous behaviors, and loses credibility. Next comes the neglect of geometric design, because even the best traffic lights cannot compensate for a poorly designed intersection. Then there is the forgetting of accessibility from the very beginning of the design, which leads to costly modifications. Thinking about design and functionality together is the first rule.

What management errors expose to danger?

From an operational standpoint, the main error is the lack of structured preventive maintenance. Waiting for a breakdown to intervene on equipment whose failure creates an immediate danger is unsustainable. Another flaw is neglecting sound repeaters, whose failure excludes visually impaired pedestrians and constitutes a non-compliance. Finally, managing without traceability deprives one of any proof of due diligence. In this area, these errors affect safety and liability. The NF P99-050 standard and traceable monitoring are the antidote.

What errors affect accessibility?

Equipping a traffic light with a sound repeater is not enough: it must also be kept in good working condition. A silent, poorly adjusted, or incomplete repeater is a non-conformity that excludes blind or visually impaired pedestrians. Neglecting these devices, forgetting to update their messages with location information, are frequent and serious errors. Accessibility is not an option; it is an obligation that must be actively maintained. Regularly checking the repeaters is an integral part of maintaining a compliant intersection.

Innovations and Trends in Traffic Signals

Does traffic signal technology continue to innovate? Much more than one might imagine. Between LED, adaptive control, centralized networks, enhanced accessibility, and the perspective of connected vehicles, the sector is modernizing rapidly, driven by the challenges of safety and mobility. A look at the developments shaping tomorrow's traffic lights.

What has changed with the switch to LED?

The most visible revolution is that of LED. LED light heads have largely replaced the old incandescent bulbs, and for good reasons. They consume much less energy, last much longer, and offer better visibility, including in full sunlight. This technology has transformed the economy and reliability of traffic signals.

The LED also has an impact on maintenance. A LED head fails less often than a bulb, extending replacement intervals. However, its brightness declines gradually, and its optical compliance must be monitored over time. Monitoring remains therefore necessary, albeit in a different form. On site, the switch to LED has reduced the most frequent failures, while shifting attention to the control of light performance. A major advancement for reliability.

How do the lights adapt to traffic?

Adaptive regulation is gaining ground. Instead of fixed cycles, smart traffic lights adjust their phases in real time according to actual traffic, measured by loops or sensors. This adaptation smooths traffic flow, reduces unnecessary waiting times, and limits superfluous stops. An adaptive intersection better manages traffic flow variations, whether during peak hours or off-peak times.

This intelligence extends to the scale of a city. Centralized networks allow the control of all intersections within an urban area from a traffic management center, coordinating traffic lights to smooth the flow along major routes. This comprehensive management optimizes traffic on a large scale. However, it adds technical complexity and vulnerability, which we will return to. Adaptive and centralized regulation represents a major technological leap for traffic signaling.

What cybersecurity challenges for connected traffic lights?

The connection of traffic lights raises a new challenge: cybersecurity. A centralized network of intersections, remotely controlled, becomes a potential target. Cybersecurity authorities have issued enhanced requirements for agglomerations with centralized networks and global traffic light management terminals. Protecting these systems against hacking has become a necessity.

This dimension transforms maintenance. Beyond the physical upkeep of equipment, data, servers, and communications must now be secured. Data generated at intersections is transmitted to control centers, and soon to connected vehicles. This data flow calls for new protocols and maintenance interventions on computer systems. Cybersecurity has become a component of modern traffic light management. A challenge that will only grow.

How is accessibility progressing?

The accessibility of traffic signals continues to improve. Sound repeaters, now mandatory on R25 signals, now include location information in their messages, indicating the name of the crossed street. Devices are evolving, with more advanced repeaters, sometimes vandal-proof. The goal: that no pedestrian, regardless of their disability, is excluded from the intersection.

This inclusion meets a legal and ethical requirement. An accessible intersection must function for everyone, both sighted and visually impaired. Innovations in repeaters and guidance systems bring us closer to this ideal. On the ground, the deployment and, especially, the maintenance of these equipment are progressing, driven by accessibility requirements. Accessible luminous signage is not an addition, it is an essential component of a compliant intersection. And its maintenance is a full-fledged obligation.

Accessibility of traffic signals: an imperative to maintain

The accessibility of pedestrian signals deserves a dedicated development, as it is both central and demanding. Beyond installation, it is the maintenance of these devices that makes all the difference for visually impaired pedestrians. Decoding a major challenge, often underestimated.

Why are sound repeaters essential?

For a blind or visually impaired pedestrian, the visual traffic light is of no use. The audible repeater is their only means of knowing whether they can cross. This device verbally announces the traffic light phase, allowing or disallowing crossing. Without it, the visually impaired pedestrian is deprived of vital information and exposed to real danger. The audible repeater is therefore an essential safety equipment, not just a comfort.

The regulation has clearly understood this, by making these repeaters mandatory on R25 lights. However, the obligation does not stop at installation. The regulation requires that these equipment be kept in good working condition. A repeater that is installed and then left inoperative no longer fulfills its function and constitutes a non-compliance. Therefore, maintaining the equipment in good condition is just as important as the initial installation. It is an ongoing obligation, relying on regular maintenance.

How to maintain sound repeaters?

Maintaining repeaters requires regular and precise checks. During inspections, the figurine's equipment, the proper functioning of the electronic card, the receiver, and the speaker, as well as the conformity of messages and sound volume are verified. Every detail matters: an incomplete message, too low a volume, a faulty speaker, and the device no longer fulfills its role.

This monitoring connects to the general maintenance of the intersection. Checking the repeaters is added to the inspection of the heads, the controller, and the electrical components. A well-maintained repeater park ensures the accessibility of all equipped intersections. On the contrary, neglected repeaters exclude visually impaired pedestrians and expose the manager. Tracing these checks via a tracking tool allows ensuring and proving the maintenance of accessibility. On this sensitive topic, rigor is doubly necessary, for inclusion and for compliance.

How to properly install lights for accessibility?

The placement of supports directly affects accessibility. The positioning of lights can enhance or impair the perception of sound signals by blind or visually impaired pedestrians. It also influences the understanding of the intersection's geometry. Proper placement helps visually impaired pedestrians to orient themselves and cross safely. Technical organizations have indeed established precise recommendations on this matter, resulting from studies conducted with visually impaired individuals. Considering accessibility from the outset and maintaining it thereafter is essential for real inclusion at the intersection. It is an expert's work, where every detail matters for the safety of the most vulnerable.

History and Evolution of Traffic Signals

To understand today's fires, a detour through their history sheds much light. These equipment have evolved significantly, in step with the automobile, electronics, and concerns about safety and accessibility. A small journey through time, instructive for those who want to grasp today's challenges.

Where do traffic lights come from?

Traffic signals were born with the explosion of automobile traffic. As cities became more densely populated and the number of cars increased, the need to regulate intersections became essential. In France, the first traffic light was installed in Paris in 1923, a small revolution in urban traffic management. Since then, these devices have spread throughout all urban areas.

The initial principle was simple: alternating traffic flows using different colors. But the technique quickly became more sophisticated. Controllers appeared, then improved, evolving from simple mechanisms to electronic automatons. Regulation, initially based on fixed cycles, became adaptive. From a rudimentary device, the traffic light has become a complex and intelligent system. This evolution accompanies the growth of traffic and the demand for safety.

How has technology transformed traffic lights?

The technique has transformed the lights. Incandescent bulbs, once the standard, have given way to LED, which are more durable and energy-efficient. Controllers have become smarter, incorporating traffic detection and adaptive regulation. Accessibility has made its entrance, with sound repeaters for visually impaired pedestrians. Each advancement has reinforced safety, efficiency, or inclusion.

This evolution continues today. Centralized networks, connected traffic lights, the prospect of autonomous vehicles communicating with intersections: traffic signals continue to transform. Moving from an isolated system, they have become a link in a connected mobility ecosystem. This trajectory, driven by continuous innovation, reflects the importance of intersections in urban traffic. The traffic light, once simple, has become a field of high technology.

What future for traffic signals?

The future is written around three words: intelligence, connectivity, inclusion. Intelligence, with adaptive regulation and the optimization of flows. Connectivity, with communicating vehicles and centralized networks. Inclusion, with continuously reinforced accessibility. Three dynamics that are transforming the traffic light intersection into an evolving piece of infrastructure at the heart of tomorrow's urban mobility. Some cities are even rethinking the role of traffic lights, in favor of alternative arrangements, a sign of a field in constant questioning.

Light signaling and traffic regulation: challenges and limitations

Traffic lights are not a miracle solution. Although they effectively regulate traffic, they also have limitations and drawbacks that need to be known. Understanding these issues helps use them appropriately. A subject more nuanced than it appears.

When is a traffic light intersection justified?

A traffic light intersection is justified in specific situations. It is particularly well suited for managing dense and fast traffic on major urban routes. It facilitates the merging of vehicles coming from secondary routes, ensures pedestrian crossing safety, and organizes complex traffic flows. On a busy intersection, it brings order and security.

But its implementation must be justified. Installing traffic lights without a valid reason can lead to negative consequences: unnecessary waiting times, loss of credibility, and dangerous behaviors. A simple objective of speed moderation, for example, is not sufficient to justify traffic lights. The relevance of the implementation is therefore crucial. A well-placed intersection with traffic lights enhances safety; a poorly placed one is annoying and can even worsen the risks. Judgment is essential.

What are the disadvantages of traffic lights?

Traffic lights have their drawbacks. They generate waiting times, sometimes perceived as unnecessary, for both vehicles and pedestrians. A poorly timed traffic light can encourage dangerous behaviors, such as crossing on yellow or red. And an intersection with traffic lights does not guarantee the absence of accidents, far from it, as accident statistics show.

These limitations explain why some cities are rethinking their intersections. Roundabouts, shared spaces, and meeting zones: alternatives exist, sometimes more fluid and safer in certain contexts. Traffic lights remain a valuable tool, but not universal. Their use must result from a careful analysis of the intersection and its uses. When properly used and well-timed, they enhance safety; when misused, they can be counterproductive. The right tool in the right place is the principle.

How to ensure the credibility of alarms?

The credibility of a traffic light is essential to its observance. If users perceive a light as unjustified or poorly timed, they are tempted not to follow it, which creates danger. Excessive waiting times, a red light that seems unnecessary, and the temptation to ignore it increase. Maintaining credibility requires relevant timing and consistent proper functioning.

Maintenance plays a key role here. A reliable, well-adjusted light that operates without failure inspires respect. On the contrary, a light that is often out of order or poorly timed loses credibility, and with it, effectiveness. Ensuring the permanent proper functioning of lights is therefore also ensuring their respect by users. Technical reliability feeds credibility, which in turn feeds safety. Everything is connected, and maintenance is at the heart of this virtuous chain.

Glossary of Traffic Signals

To close this guide, here is a glossary of the cross-referenced terms throughout the article. Handy to have on hand when facing a specification sheet or a public tender.

• Signal light : luminous device regulating traffic at intersections.
• SLT : tricolor light signaling.
• Signalized intersection : intersection controlled by traffic lights operated by a controller.
• Controller : automaton managing the phases of the intersection.
• Headlight : luminous element, today most often LED.
• R11 : traffic light for vehicles at an intersection.
• R12 and R25 : pedestrian signals, the R25 with sound repeater.
• Sound Repeater : accessibility device for the blind and visually impaired.
• Phase : period during which a set of movements is authorized.
• Clearing Time : time required to clear the intersection between two flows.
• NF EN 12368 : fire head standard.
• NF EN 12675 : functional safety standard for controllers.
• NF P99-050 : standard for the principles of traffic light intersection maintenance.
• ASCQUER : lighting equipment certification body.
• IISR 6th Part : reference text on permanent traffic signals.

How to control the cost of a traffic light network?

A traffic light intersection park represents a heavy investment and recurring operating costs. Heads, controllers, repeaters, energy, interventions: these expenses can be managed. Well managed, they ensure availability and safety at the best cost. Decoding the levers that prevent waste while protecting the manager.

Which positions contribute to the cost of fires?

The cost of a traffic light network consists of several components. First, the acquisition and installation of the intersections, heavy-duty equipment. Then, energy consumption, reduced by switching to LED. Next, maintenance, both preventive and corrective, including emergency interventions, replacement of bulbs, and troubleshooting of controllers. Over time, maintenance and equipment renewal weigh heavily.

Preventive maintenance, once again, reduces the overall cost. By anticipating breakdowns, we avoid emergency interventions, which are always more expensive, and especially dangerous situations. The switch to LED has also reduced the energy bill and the frequent replacement of bulbs. A well-managed fleet, compliant with NF P99-050, is cheaper than a neglected fleet that multiplies breakdowns and exposes to liability. The rigor of monitoring is a profitable investment, not a burden.

How to optimize maintenance interventions?

Mobility and interventions represent major positions, especially on an extensive fleet. Optimizing routes means reducing mileage and grouping preventive checks. Geolocation of junctions and planning allow effective coverage of the fleet, while reserving reactivity for emergencies. As for parts, knowing your fleet prevents stockouts and dormant inventory.

An intervention tracking tool is precisely designed for this purpose. By consolidating the status and history of each intersection, it enables the planning of preventive maintenance, grouping of inspections, and prioritization of at-risk equipment. Data transforms a reactive management approach into an organized one, thus reducing costs. On a large number of intersections, this logistical gain is far from trivial. It is often there that the greatest savings are achieved, without compromising safety.

When to replace rather than repair equipment?

The issue of renewal arises when a controller or components accumulate failures or age. The sound decision is based on data: an equipment with a traceable history, including its failure history and cumulative maintenance costs, is replaced at the right time. Rather than persisting with a capricious controller, its renewal is decided when the calculation justifies it, taking into account the safety implications. An unreliable equipment at an intersection must be replaced without hesitation, as its real cost includes the risk it poses. Data illuminates this decision, transforming intuition into a rational and secure choice.

How to optimize the availability of a traffic light intersection?

Availability is the key word in traffic light management. An intersection can only fulfill its mission if it operates continuously. Maximizing this availability through rigorous organization is the central objective of the manager. Decoding the concrete levers.

Why is availability the key indicator?

A traffic signal is only valuable if it is functioning when users rely on it. An intersection that is frequently out of service, or whose repeaters are silent, provides a failing and dangerous service. The real value of a park is measured by its availability rate, not by the number of intersections. Maintaining a high availability rate through preventive maintenance and prompt response to failures is the essence of the job. An available intersection protects; a failed intersection endangers.

This availability has an absolute safety dimension. On a panel, a degradation can wait for a few days. On a fire, the failure creates an immediate danger that requires immediate intervention. Availability is therefore not just a simple quality indicator, but a safety condition. The entire challenge of fire maintenance lies in guaranteeing this permanent availability, day and night, including weekends.

How to reduce response times?

Reactivity depends on organization. A dedicated team for critical breakdowns, available spare parts, and qualified technicians evenly distributed allow for quick intervention. Geolocation and precise knowledge of each intersection speed up diagnosis and repair. The shorter the time between the breakdown and restoration, the more limited the danger. Reducing this time is an absolute priority in this field.

Digital tools transform this responsiveness. A reported breakdown, geolocated, with the intersection's history accessible to the technician, allows for a faster and better prepared intervention. The technician knows what to bring, where to go, and what has already been done. On site, this preparation saves precious time. Integrating reports, tracking, and history into a single tool, like KARTES, directly optimizes response times. And on traffic lights, every minute gained reduces the danger at the intersection.

How to ensure preventive maintenance?

Preventive maintenance is the best way to avoid breakdowns. But it is only effective if it is actually applied, on time and according to the periodicities of NF P99-050. Too often, preventive checks are postponed due to lack of follow-up, until a breakdown occurs. A work order management tool ensures that every scheduled inspection is carried out and documented, without any omissions. It turns preventive maintenance from an intention into an effective and documented practice. On a network of traffic signals, where prevention determines safety, this guarantee is invaluable. Plan, execute, document: this is the triad of a truly implemented preventive maintenance, which maximizes the availability and safety of intersections.

10 Frequently Asked Questions About Traffic Lights

What is a traffic light?

A traffic light, or traffic signal, is a luminous device that regulates traffic at intersections by alternating green, yellow, and red. It is part of a system controlled by a controller, which separates in time the flow of vehicles and pedestrians to avoid conflicts.

What is a traffic light intersection?

A traffic light intersection is an intersection where traffic is controlled by signal lights operated by a controller. This controller coordinates the phases, deciding when each light turns green, yellow, or red, according to a fixed program or by adapting to actual traffic conditions.

What is the minimum green light duration of a traffic light?

According to the Interministerial Instruction on road signage, the minimum green time is 6 seconds, although 10 seconds are preferable. The maximum waiting time for a road user should not exceed 120 seconds, in order to preserve the credibility and respect of the traffic light.

Should pedestrian signals be audible?

Yes, pedestrian R25 signals must be equipped with audible repeaters, which have been mandatory since the decree of April 2, 2012. These devices verbally announce the traffic light phase to blind or visually impaired individuals. They must indicate the location and be kept in good working condition.

Which standard governs the fire heads?

The NF EN 12368 standard governs fire heads: optical characteristics, environmental resistance, CE marking. Since February 1, 2009, circular signals of 200 or 300 mm must bear the CE marking. ASCQUER is the notified body responsible for their certification in France.

Who is responsible for traffic lights?

The road manager, whether a municipality or metropolitan area, is responsible for the proper functioning and compliance of its traffic lights. A malfunctioning traffic light creates an immediate danger and may engage its liability in case of an accident. Maintenance in accordance with the NF P99-050 standard and its traceability are essential.

What does a flashing yellow light mean?

A flashing yellow light indicates that the intersection traffic lights are out of service or in degraded mode. Users must then exercise extra caution and apply normal priority rules, as in an intersection without traffic lights. It is a safety mode activated in case of failure.

Which standard governs the maintenance of traffic lights?

The NF P99-050 standard, revised in 2018, deals with the principles of maintaining traffic signal intersections. It defines maintenance actions and their frequency, service condition levels, and response times. It helps in drafting a precise maintenance specification.

Why is a faulty fire alarm dangerous?

Unlike a degraded sign, a malfunctioning traffic light creates an immediate danger at the intersection. A turned-off light or a failing controller causes confusion and accident risk for both vehicles and pedestrians. This is why the response time for intervention is a vital criterion for traffic light maintenance.

How to maintain a traffic light intersection park?

The maintenance combines preventive maintenance in accordance with NF P99-050, inspection of heads, diagnosis of controllers, verification of sound repeaters and electrical installations. A preventive approach, based on a geolocated inventory and traced tracking, ensures availability, accessibility, and compliance.

Conclusion: traffic signals, a critical equipment to maintain without fail

We have seen throughout this guide that traffic signals are not just mundane equipment. Behind every signalized intersection lie a controller, LED heads, sound repeaters, strict regulations (IISR 6th part, NF EN 12368, NF P99-050), and a strong responsibility from the manager. It is a critical safety equipment, and even the slightest failure creates an immediate danger at the intersection.

Maintenance, and particularly preventive maintenance in accordance with NF P99-050, makes all the difference between a reliable, safe, and accessible network, and a set of intersections that fail at the worst moment. Diagnose, inspect, quickly resolve issues, maintain repeaters, track: these are the keys. And to orchestrate all of this without getting overwhelmed, while protecting yourself legally, an intervention tracking application like KARTES transforms the management of a fire network into data-driven control, benefiting local authorities, maintainers, users, and residents.

You manage a network of traffic lights, are you a technician, elected official, or network manager? Take a few minutes to assess how the status, availability, and accessibility of your traffic lights are currently being monitored. If the answer lies in scattered documents, there is certainly a better way to do things, and your responsibility is at stake. Share this guide with others; it could illuminate your next maintenance project.

At bottom, a traffic light is judged only at one moment: when a pedestrian steps out, or a driver crosses the intersection, relying on the light. Everything else, the technology, the standards, the programming, is only valuable if, at that moment, the light works and tells the truth. Ensuring this moment, through rigorous and documented maintenance, is the very essence of the job. Keeping traffic lights well-maintained is simply ensuring, intersection after intersection, the safety of everyone who travels, day after day.

Finally, keep in mind a simple idea: at traffic lights, the real difference is not in the installed equipment, but in the rigor with which preventive maintenance and long-term availability are ensured. Two communities equipped with the same intersections can offer completely opposite levels of safety and face completely different legal risks, depending on whether they maintain and mark according to NF P99-050 or wait for a breakdown. Geolocated inventory, preventive checks, tracking of sound repeaters, responsiveness to breakdowns, documented maintenance proof: these fundamentals, modest but decisive, ensure the safety and compliance of a fleet. The rest—manufacturers, technologies, programming—is only the foundation of a public service that is only valuable through the consistency of its maintenance and the solidity of its traceability, on equipment where every failure can be costly.