In , Lester Wire, a young police officer in Salt Lake City, came up with an idea. What if there was a tool to regulate cars at intersections instead of patrol officers, who needed to spend hours rooted to a platform through rain, heat, and hail?
Wire came up with a wooden box on a pole. It had two light bulbs inside, colored red and green. The box was connected to electricity so the light bulbs could be switched from one to the other with the press of a button. That&#;s something patrol officers could do from a booth at the side of the road.
Since then, traffic light signals have evolved a bit. We now have yellow and don&#;t need a patrol officer to press a button. But the original concept has remained largely the same &#; traffic lights change on a pre-programmed schedule.
However, the state of our roads in the twenty-first century is much different than it was 100 years ago. We have more cars, bigger road networks, higher population densities, and constant traffic disruptions.
Perhaps it&#;s time to rethink the old and introduce a smarter traffic light system.
A smart traffic light is an internet-connected vehicle traffic control system capable of adapting traffic light controls based on information collected from sensors, edge devices, and video systems.
At the intersection, smart traffic lights look the same as regular traffic lights except for extra hardware elements such as IoT sensors and/or connected CCTV cameras. On the back end, smart traffic light systems are connected to a cloud-based traffic management platform. They are often powered by predictive algorithms for dynamically adjusting traffic signals.
A quick disclaimer before we go any further: A smart traffic light system can&#;t miraculously fix all road issues, such as congestion, accidents, and rule violations. But they are a better preventive measure than traditional traffic lights.
As Dan Saffer, an author and the Creative Director at Smart Design, says:
Traffic lights are only a mechanical prop, a signifier of a social contract we&#;ve agreed to (and have written into law).
Apart from a potential fine (and good conscience), nothing stops people from red-light running (RLR) on empty intersections &#; and drivers do that a lot. In New York City, more red-light violations were recorded in than in any year since . Accident rates also went up, which is problematic.
Why do people violate traffic signal rules?
Scientists agree that violations are highly contextual. The exact reasons vary, but they often fall into one of these categories:
Smart traffic light systems cannot fully discourage people from breaking traffic rules, but they can make it less tempting.
With adaptive traffic signal control (ATSC), you can program dynamic rules for signal changes based on conditions and better detect RLR at busy intersections. Smart traffic signs can also adjust recommended speed limits based on the weather or road conditions to improve traffic throughput. Intelligent traffic lights, in turn, can adjust signal timing based on the volume of vehicles at different intersections and variable factors such as the time of day. Such a setup can ensure smooth traffic flows and reduce the number of situations when breaking traffic rules seems appealing (or undetectable).
For city managers, intelligent new traffic lights are a much-needed alternative to manual or rule-based signal controls.
Many cities operate traffic management centers that are hives of activity akin to a busy urban air traffic control operation. But appearances are somewhat deceiving, given that the traffic engineers have limited tools available to manipulate their signal networks to respond in real-time.
Urban traffic managers can (and should) integrate smart signaling into an intelligent transportation system. Merging the two enables users to exercise algorithmic, context-driven control over the city&#;s transport grid through one interface. The best part? Digital traffic signals can be dynamically adjusted in real time across the entire network to:
That&#;s some blissful city to live in, right?
Sadly, only a fraction of new traffic signals today are smart. Traffic light hardware can last for up to 30 years if well-maintained. But among new traffic signals, few are (or can be) connected to cameras, radar systems, or sensors. And those that do have basic sensing capabilities often can&#;t detect cyclists or pedestrians.
Fortunately, this is changing. Urban planners &#; and the general public &#; realize that standard traffic light systems need extra wits as more connected cars and electric commercial fleets hit the roads.
As part of a £30m investment in better urban connectivity, the city of Manchester is testing an AI traffic lights system. The city is installing a network of edge devices for collecting real-time road data on each junction and plans to use 5G technology for dispatching data to the cloud for analysis.
London, in partnership with Siemens, is testing a real-time adaptive traffic signals control (ATSC) solution called Sitraffic FUSION that is powered by data from connected vehicles and connected road infrastructure. Sitraffic FUSION can detect, model, and optimize routes for all modes of transport around the set KPIs. The system also includes a traffic light algorithm for optimizing controls on signalized junctions and pedestrian crossings.
Many more cities are looking into modernizing their traffic controls &#; and that means plenty of opportunities for new market entrants.
Smart traffic signals are equipped with sensing, video capture, and connectivity technologies to collect real-time data from the environment. The obtained data is either pre-processed on the device or transmitted to a cloud-based transport management system, where it&#;s processed by a predictive traffic light algorithm that generates instructions for signal adjustments.
A standard smart traffic light system has two elements:
A smart roadside traffic light unit still has the familiar three-light interface &#; and some extra goodies.
The exact configuration differs by manufacturer. Some smart traffic lights have more advanced sensing capabilities; others just rely on camera footage. NoTraffic, for example, uses IoT sensors that rely on radar and computer vision for smart signaling and also captures car data in C-V2X and DSRC formats.
On the software side, a smart traffic light system can process data in two ways: on-device (on the edge) or in a cloud location.
On-edge road data pre-processing reduces latency. With suitable hardware, you can run baseline traffic conditions analysis on a smart traffic light device. For example, such roadside units can:
On-edge processing is a pillar for implementing adaptive traffic signals control (ATSC) &#; real-time traffic signal adjustments based on the current road situation. ATSC systems can reduce average travel times by 25%, shorten signal wait times by 40%, and lower emissions by 20% according to Carnegie Mellon University.
Next, digital traffic signals can dispatch pre-processed and raw data to a connected cloud-based control center, such as an intelligent transport system (ITS). Here you can perform more advanced modeling and predictive analysis to stave off traffic congestion and harmonize public transport schedules.
Likewise, you can use historical data collected by edge devices to build advanced models for:
Smart traffic light technology adds a new dimension of real-time control &#; and many good things come as a result:
To provide the above benefits to urban planners, future traffic lights should include the following four features.
Predictive algorithms operating at the back end of a smart traffic light system can find effective solutions to complex traffic management problems. Such systems can correlate traffic signaling rules with violation or accident rates &#; and model risk-minimizing scenarios with higher precision than a human traffic manager could (plus do so in real time).
Over time, a predictive smart traffic lights system can rely on sensors and visual data alone to make on-the-spot decisions and control traffic movements.
Case in point: A group of German researchers recently collaborated with city planners in Lemgo on an AI program for traffic light management. The team used a set of high-resolution cameras and radar sensors to capture traffic data. Then they trained a deep learning algorithm to regulate signaling at a busy intersection.
The algorithm was tasked with estimating the optimal switching behavior for the traffic lights and the best phase sequence to reduce:
During the simulation run, the algorithm managed to achieve a 10% to 15% improvement in traffic throughput in the tested area.
Emergency vehicles need priority access to the roads. The chance of survival is reduced by 7% to 10% for every minute emergency medical assistance is delayed. Likewise, the consequences of delayed arrival of police, firefighters, and other emergency services can be grave.
Yet emergency vehicles often get stuck in heavy traffic where drivers have to move aside to let the emergency go through. A signaling system with a smart emergency vehicle traffic light changer can address the matter in four ways:
Case in point: A recent US study of smart traffic signal preemption for emergency vehicles found some interesting insights.
Vrooming engines at busy intersections create a layer of noise and air pollution. Plus, they make areas with busy intersections less desirable for urban dwellers &#; a factor that also affects a neighborhood&#;s economic development.
Smart traffic signals can help reduce vehicle idle time and promote more sustainable driving habits. A group of Taiwanese scientists carefully documented a set of eco-driving traffic light regulation models that can be implemented in sensor-based traffic light systems.
Eco-Driving Model Concept Actions Benefit Application MaxTM,
Source: MDPI &#; Design and Implementation of a Smart Traffic Signal Control System for Smart City Applications
Their findings have already been put into action by the PTV Group in Taipei. The PTV Balance software platform can detect changes in traffic patterns and suggest smart stop light signals for cars, cyclists, and pedestrians.
Taipei authorities tested the platform in two districts, Neihu and Nangang. The results were impressive:
Micromobility vehicles such as bikes, e-bikes, and e-scooters are a growing part of the MaaS ecosystem. But they also present extra road hazards, both for pedestrians and drivers. In the first half of , e-scooter crashes in London grew by 2,800% compared to the entirety of .
As the use of personal and shared micromobility solutions surges, their movements must be better regulated. Smart traffic light systems should factor in these road players and create better controls for them.
For maximum safety, it&#;s best to adopt a two-step mechanism:
Peek Traffic has developed an interesting smart mobility solution for regulating cyclists and pedestrians They aim to connect all road users to an intelligent traffic control system via an ITS app. The app, in turn, sends signals to a smart traffic light control system. So when a vulnerable pedestrian attempts to cross the street, the app can issue an update to a connected traffic light so that it automatically adjusts the signal lengths. The same app can also inform the traffic light system about approaching cyclists to adjust the timing for them. Such dynamic traffic lights on cycling roads make bike use more attractive, which carries lots of benefits.
The impact of smart traffic light systems extends beyond mere driver convenience; it can create a cascade of positive effects:
Given that our current traffic control systems are over a century old, updates are overdue.
Intellias is a technology partner to leading companies in the transportation sector. Contact us to receive a personalized consultation on developing smart traffic light software.
The normal function of traffic lights requires more than sight control and coordination to ensure that traffic and pedestrians move as smoothly, and safely as possible. A variety of different control systems are used to accomplish this, ranging from simple clockwork mechanisms to sophisticated computerized control and coordination systems that self-adjust to minimize delay to people using the junction.
[
edit
]
The first automated system for controlling traffic signals was developed by inventors Leonard Casciato and Josef Kates and was used in Toronto in .[1][2][3]
[
edit
]
In Australia and New Zealand, the terminology is different. A "phase" is a period of time during which a set of traffic movements receive a green signal - equivalent to the concept of a "stage" in UK and USA. One electrical output from the traffic signal controller is called a "signal group" - similar to the UK and USA concept of "phase". PTV VISSIM also uses the signal group terminology.
[
You will get efficient and thoughtful service from FAMA.
edit
]
This three-arm signal controlled junction has three vehicle phases (A, B and C) and a pedestrian phase (D). The phases operate together in three stages (1, 2 and 3). Moving phases are shown in green and stopped phases are shown in red.Phases are indications shown to traffic on traffic signal aspects (a single light on a signal head). For example, a green phase gives all traffic from a particular approach the right of way through the junction (bar turning traffic). In the UK, a filter phase allows non-conflicting traffic to make particular turns (normally left or ahead) through a junction.[4][5][6]
A movement is any path through the junction which vehicles or pedestrians are permitted to take. A movement is conflicting if these paths cross one another. Normally, conflicting movements are not permitted, except for opposed right or left turns (depending on driving side) or, in some jurisdictions, pedestrians and vehicles moving in parallel directions.[4]
[
edit
]
A stage is a group of non-conflicting phases which move at the same time.[7][4] For example, a crossroads with four approach arms could operate in two-stage operation, where each road is given green, or three-stage operation, where the major road is given green, then each side road is given green in turn. A cycle is one complete sequence of stages. The cycle time is the time it takes for a cycle to complete. Some jurisdictions have maximum cycle times. For example, in the UK this is 120 seconds or 90 seconds where pedestrian facilities are present. Under actuated control, the reversion is the stage which the traffic controller will return to if there is no demand.[4]
The interstage or intergreen period is the period between the end of a green signal in one phase and the start of a green signal in the next phase. This normally includes an amber signal on approaches where the green phase is ending and an all red stage, where all signals which are changing are red to allow the junction to clear. All red stages produce lost time, where no road users can proceed through the junction.[4][8]
An interval is the period between changes in signal stages. For example, the vehicular green interval is the period of time that vehicular traffic has a green signal. The interval is fixed in pre-timed control and varied in actuated control. In actuated settings, the minimum interval in the minimum amount of time for which a signal will stay green before changing. This can be as low as 2 seconds for local roads, but may need to be up to 15 seconds for arterial roads. The maximum interval is the maximum amount of time one road will be allowed a green signal, where demand is present on another road.[4][9]
For pedestrians, an invitation period is the period of time where pedestrians are invited to begin crossing the road. This is normally shown with a green or white male walking figure.[4]
[
edit
]
A traffic signal is typically controlled by a controller mounted inside a cabinet.[10] Some electro-mechanical controllers are still in use (New York City still had 4,800 as of , though the number is lower now due to the prevalence of the signal controller boxes[11]). However, modern traffic controllers are solid state. The cabinet typically contains a power panel, to distribute electrical power in the cabinet; a detector interface panel, to connect to loop detectors and other detectors; detector amplifiers; the controller itself; a conflict monitor unit; flash transfer relays; a police panel, to allow the police to disable the signal; and other components.[10]
Computerized traffic control boxIn the United States, controllers are standardized by the NEMA, which sets standards for connectors, operating limits, and intervals.[10] The TS-1 standard was introduced in for the first generation of solid-state controllers.[12]
Solid state controllers are required to have an independent conflict monitor unit (CMU), which ensures fail-safe operation. The CMU monitors the outputs of the controller, and if a fault is detected, the CMU uses the flash transfer relays to put the intersection to FLASH, with all red lights flashing, rather than displaying a potentially hazardous combination of signals. The CMU is programmed with the allowable combinations of lights, and will detect if the controller gives conflicting directions, for instance, green signals facing both northbound and eastbound traffic at a cross intersection. Conflict monitors are susceptible to false activation during thunderstorms due to power surges and noise induced by nearby lightning strikes.
In the late s, a national standardization effort known as the advanced transportation controller (ATC) was undertaken in the United States by the Institute of Transportation Engineers.[12] The project attempts to create a single national standard for traffic light controllers. The standardization effort is part of the National Intelligent transportation system program funded by various highway bills, starting with ISTEA in , followed by TEA-21, and subsequent bills. The controllers will communicate using National Transportation Communications for ITS Protocol (NTCIP), based on Internet Protocol, ISO/OSI, and ASN.1.[12]
Battery backups installed in a separate cabinet from the traffic controller cabinet on the top.Traffic lights must be instructed when to change stage and they are usually coordinated so that the stage changes occur in some relationship to other nearby signals or to the press of a pedestrian button or to the action of a timer or a number of other inputs.
[
edit
]
In the areas that are prone to power interruptions, adding battery backups to the traffic controller systems can enhance the safety of the motorists and pedestrians. In the past, a larger capacity of uninterruptible power supply would be required to continue the full operations of the traffic signals using incandescent lights. The cost for such system would be prohibitive. After the newer generations of traffic signals that use LED lights which consume 85-90% less energy, it is now possible to incorporate battery backups into the traffic light systems. The battery backups would be installed in the traffic controller cabinet or in their own cabinet adjacent to the controller.
The battery backups can operate the controller in emergency mode with the red light flashing or in fully functional mode. In , California Energy Commission recommended to have local governments to convert their traffic lights to LEDs with battery backups. This would lower the energy consumption and enhance the safety at major intersections. The recommendation was for a system which provides fully functional traffic signals for two hours after the power outage. Then the signals will have flashing red lights for another two hours.[13]
[
edit
]
There are a number of types of control mechanisms for junctions controlled by traffic signals:
Type Meaning Conditions Example use Isolated pre-timed Fixed cycle length For temporary operation, where detection not available Roadworks Coordinated pre-timed Fixed cycle length Where traffic is consistent City centres, interchanges Semi-actuated No fixed cycle length, defaults to one movement Traffic imbalance - Highway operations Fully-actuated No fixed cycle length, detection used on all approaches, responsive to conditions Where detection used on all roads Rural, high speed locations or two arterial roads Coordinated actuated Fixed cycle length Heavy traffic on arterial roads Suburban arterial[
edit
]
Pedestrian traffic signal in Taiwan, featuring a "Walking green man" below a countdown display where the "Red Man" once stood.In traffic control, simple and old forms of signal controllers are what are known as electro-mechanical signal controllers. Unlike computerized signal controllers, electro-mechanical signal controllers are mainly composed of movable parts (cams, dials, and shafts) that control signals that are wired to them directly. Aside from movable parts, electrical relays are also used. In general, electro-mechanical signal controllers use dial timers that have fixed, signalized intersection time plans. Cycle lengths of signalized intersections are determined by small gears that are located within dial timers. Cycle gears, as they are commonly known, range from 35 seconds to 120 seconds.[citation needed] If a cycle gear in a dial timer results in a failure, it can be replaced with another cycle gear that would be appropriate to use. Since a dial timer has only one signalized intersection time plan, it can control phases at a signalized intersection in only one way. Many old signalized intersections still use electro-mechanical signal controllers, and signals that are controlled by them are effective in one way grids where it is often possible to coordinate the signals to the posted speed limit. They are however disadvantageous when the signal timing of an intersection would benefit from being adapted to the dominant flows changing over the time of the day.[14]
[
edit
]
Diagram demonstrating that when traffic lights are synchronised for traffic travelling in one direction (green arrows), the traffic in the other direction is not necessarily synchronised (blue arrows).Attempts are often made to place traffic signals on a coordinated system so that drivers encounter a green wave&#;&#;&#;a progression of green lights. The distinction between coordinated signals and synchronized signals is very important. Synchronized signals all change at the same time and are only used in special instances or in older systems. Coordinated (progressed) systems are controlled from a master controller and are set up so lights "cascade" (progress) in sequence so platoons of vehicles can proceed through a continuous series of green lights. A graphical representation of phase state on a two-axis plane of distance versus time clearly shows a "green band" that has been established based on signalized intersection spacing and expected vehicle speeds.[15] In some countries (e.g. Germany, France and the Netherlands), this "green band" system is used to limit speeds in certain areas. Lights are timed in such a way that motorists can drive through without stopping if their speed is lower than a given limit, mostly 50 km/h (30 mph) in urban areas. This system is known as "grüne Welle" in German, "vague verte" in French, or "groene golf" in Dutch (English: "green wave"). Such systems were commonly used in urban areas of the United States from the s, but are less common today. In the UK, Slough in Berkshire had part of the A4 experimented on with this. Many US cities set the green wave on two-way streets to operate in the direction more heavily traveled, rather than trying to progress traffic in both directions. But the recent introduction of the flashing yellow arrow (see article Traffic-light signalling and operation) makes the lead-lag signal, an aid to progression, available with protected/permissive turns.[15][16]
In modern coordinated signal systems, it is possible for drivers to travel long distances without encountering a red light. This coordination is done easily only on one-way streets with fairly constant levels of traffic. Two-way streets are often arranged to correspond with rush hours to speed the heavier volume direction. Congestion can often throw off any coordination, however. On the other hand, some traffic signals are coordinated to prevent drivers from encountering a long string of green lights. This practice discourages high volumes of traffic by inducing delay yet preventing congestion or to discourage use of a particular road. This is often done at the request of local residents in areas that have a lot of commuter "just passing through" traffic. Speed is self-regulated in coordinated signal systems; drivers traveling too fast will arrive on a red indication and end up stopping, drivers traveling too slowly will not arrive at the next signal in time to utilize the green indication. In synchronized systems, however, drivers will often use excessive speed in order to get through as many lights as possible.
This traffic light in Khobar, Saudi Arabia is video camera-actuated (just above the vertically-aligned lenses) and also shows the seconds remaining to change to the next state (in the leftmost horizontally-aligned lens)More recently even more sophisticated methods have been employed. Traffic lights are sometimes centrally controlled by monitors or by computers to allow them to be coordinated in real time to deal with changing traffic patterns.[17] Video cameras, or sensors buried in the pavement can be used to monitor traffic patterns across a city. Non-coordinated sensors occasionally impede traffic by detecting a lull and turning red just as cars arrive from the previous light. The most high-end systems use dozens of sensors and cost hundreds of thousands of dollars per intersection, but can very finely control traffic levels. This relieves the need for other measures (like new roads) which are even more expensive.
Benefits include:[18][19]
[
20]
Examples:
[
edit
]
RFID E-ZPass reader attached to the pole and its antenna (right) used in traffic monitoring in New York City by using vehicle re-identification method[
edit
]
[
31]
[
32]
[
edit
]
Traffic light systems are designed using software such as LINSIG, TRANSYT, CORSIM/TRANSYT-7F or VISSIM.
[
edit
]
In the US, there are the following handbooks:
[
edit
]