Emergency vehicles need to reach their destinations as quickly and safely as possible. However, traffic signals can delay their progress and increase the risk of collisions. How can you optimize traffic signals for emergency vehicles? In this article, you will learn some basic concepts and methods of traffic signal design and optimization for emergency response.
Traffic signals have different phases and cycles that control the flow of vehicles and pedestrians at intersections. A phase is a part of the cycle that allows a specific movement or direction of traffic. A cycle is the total time it takes for all phases to complete. The length and order of phases and cycles depend on factors such as traffic volume, speed, demand, and coordination. To optimize traffic signals for emergency vehicles, you need to understand how they affect the travel time and safety of emergency vehicles.
Important is not to stop traffic in case of emergency vehicles on the road. Traffic must be redirect to right direction to offload traffic of emergency spot and to allow traffic flow for emergency vehicle to get there.
This was looked at over 15 years ago and was called “blue wave”. Apart from some of the issues identified in this post, one of the main challenges identified was where emergency vehicles on blue lights were approaching the same junction from different directions, who would have the priority?
- une chose trouvée utile : que les cycles des feux soient adaptés au trafic réel et en fonction des cycles journaliers - un constat : des ronds points lorsque les flux sont très différents d’une branche à l’autre ne peuvent pas être efficaces, idem pour 2 ronds points trop proches. - les feux sont rarement bien acceptés par les automobilistes qui sont à l’arrêt alors qu’ils préfèrent rouler même lentement … cela ne les pas avancer plus vite très souvent
Much will depend on how occupied the intersection is. If traffic is low, it is enough to enable priority for emergency vehicles. If the traffic is high, then it is better to think about how to quickly de-occupy the direction in which the emergency vehicle is moving
Emergency vehicle preemption (EVP) is a system that allows emergency vehicles to communicate with traffic signals and request priority service. EVP can reduce the delay and improve the reliability of emergency vehicles by changing the traffic signal phases and cycles according to their needs. For example, EVP can extend the green time for the approaching emergency vehicle, shorten the red time for the conflicting traffic, or create a green wave along the emergency route. EVP can also reduce the number of stops and conflicts for emergency vehicles, which can lower the fuel consumption, emissions, and crash risk.
We don't use EVP in the UK. Traditionally, a manual switch was located inside the fire/ambulance station to place a 'Hurry Call' to the traffic signals along the route. In urban environments, most signalised traffic installations are controlled centrally from the Urban Traffic Control centre for the locality, so emergency vehicles leaving their stations can have a demand placed for their direction of travel through UTC to each set of signals.
EVP is widely used in the US, as far as I know. However, there are other approaches. For example, if a city has a unified traffic management system, all emergency vehicles can be equipped with GPS sensors or RFID tags, which will allow the traffic light to be switched when an emergency vehicle appears even 150 meters from the intersection. Or (as in the case of GPS) turn on the “green wave” mode along the route
Different types of EVP systems are used to communicate between emergency vehicles and traffic signals, such as optical, radio, and GPS. Optical systems are simple and inexpensive, but can be affected by weather, sunlight, and obstructions. Radio systems are more reliable and flexible, but can be interfered by other radio sources or devices. GPS systems are more accurate and adaptable, but require more infrastructure and maintenance. Each system has its own advantages and disadvantages, so it's important to consider the needs of your organization before selecting one.
GPS system + at least 4g data plan. With this system you can combine additional features like: - signal for "emergency drive" - system recognize when vehicle is on way to/from emergency, so can adapt traffic on vehicle road. When is not on emergency call, emergency vehicles are normal vehicles and follow rules. - using signal from turn signals/blinkers to adapt traffic flow on way of emergency vehicle. - using data from vehicle navigation to choose nearest hospital or medical center and to adapt traffic flow according route. - when emergency vehicle is on emergency call in the middle of busy street, system can redirect traffic on other routes, to cut traffic on road.
You cannot create a system as a set of standard solutions. Each region and country is different from the others in both culture and climate. For warm countries where there is no snow and little rain, I would recommend using optical systems or RFID tags due to the low cost of such solutions. But for Scandinavian countries, for example, it would be better to use systems based on GPS or radio transmitters. In addition, it is not entirely true to say that radio transmitters may not work well when there are other radio transmitters nearby. Modern industrial devices can easily automatically change their operating range when they are nearby devices operating at the same frequency.
Designing and optimizing EVP systems requires you to consider factors such as the type and location of emergency vehicles and traffic signals, the traffic signal timing and coordination plans, the traffic demand and patterns, the performance measures and objectives for emergency vehicles and general traffic, and the costs and benefits of installing and operating EVP systems. To help with this process, there are various tools and methods such as simulation, optimization, and evaluation. Simulation uses computer models to mimic the behavior and interactions of emergency vehicles, traffic signals, and general traffic. This can help test different scenarios of EVP systems and evaluate their impacts on travel time, delay, safety, and efficiency. Optimization uses mathematical models to find the best solutions for EVP systems based on performance measures. This can help determine the optimal parameters for EVP systems. Evaluation uses data to measure the performance of EVP systems. This can help monitor outcomes and identify problems or opportunities for improvement.
Adaptive signal control systems can help to automatically adapt to EVP being used by smoothing the disruption. It would be very similar to the disruption from a rail crossing or something similar. After a few cycles, traffic is back to normal.
This is true. The microsimulation process helps to significantly better understand what will happen at an intersection under a given scenario. However, with this approach it is critical that the transport model is created by professionals because only this approach allows us to make the model as close to reality as possible
EVP systems have many advantages for emergency vehicles, but they also face some challenges and limitations, such as compatibility and interoperability of different types and brands, coordination and cooperation of different agencies and jurisdictions, equity and fairness of prioritizing emergency vehicles over general traffic, and potential negative impacts on general traffic. To overcome these challenges and enhance the opportunities for EVP systems, you can develop common standards and protocols, establish partnerships and agreements among stakeholders and users, balance the needs of emergency vehicles with general traffic, and implement adaptive intelligent EVP systems that respond to real-time conditions.
Progress does not stand still. Today there are video cameras that can detect license plates at a distance of up to 300 meters. And it is very likely that soon EVP systems will simply work on recognizing license plates of emergency vehicles.
Something else to consider is that traffic signal timing and phasing has a large impact on speeds and safety throughout the corridor. While permissive left turns can be great for operations, then can also be problematic for safety. SO even if the signal timing is not able to accommodate emergency vehicles as well as we like, we can use signal timing to reduce the need for EMS to respond, at least to traffic incidents, in the first place.