Priority management saves time, money and lives

Emergency vehicle preemption systems can offer benefits to more than just first responders: mass transit and maintenance departments can also benefit from the technology.

It is difficult to over-emphasise how critical response times are to the outcomes of medical emergencies or to reduce property loss.  According to the American Heart Association, unless CPR and defibrillation is administered brain death starts within four to six minutes of a cardiac arrest, and if bystander CPR is not provided the victim’s chances of survival fall 7% to 10% for every minute defibrillation is delayed. Few attempts at resuscitation are successful if CPR and defibrillation are not provided within minutes of collapse.

In 2002 Blackwell and Kaufman undertook a comparative study of response time and survival in an urban emergency medical services system. They found the mortality risk was 0.51% for patients provided service in less than five minutes and three times as high (1.58%) for those who had to wait longer for medical attention.

There is a similar scenario with other first responders such as fire crews where it is important to reach a fire before the flashover temperature is reached because once that has happened the fire will spread extremely rapidly as various items spontaneously combust.

Travel time

A key factor in how quickly a first responder reaches an emergency is the time taken travelling to the scene - and in some cases the return trip can be almost as vital such as when taking a victim to hospital. While emergency services do their upmost to reach the scene as quickly as possible, their efforts are hampered by the growth in traffic congestion at major intersections as the population of many cities continues to expand.  To mitigate the effects of increased congestion and improve emergency vehicle response times, authorities in many cities are deploying Emergency Vehicle Preemption (EVP) systems to ensure the traffic signals turn green ahead of emergency vehicles.

According to Doug Roberts, CEO of EVP system provider 542 Global Traffic Technologies (GTT), not only can such systems reduce emergency vehicle response times by up to 25% but the benefits go much wider including reducing crashes involving emergency vehicles by up to 70%. This is because there is no need for the emergency vehicles to pass through red lights at the intersection – the situation which causes a large proportion of accidents. “In some cases the reduction in accidents means authorities in big cities can recoup the cost of the installation within a year,” he adds. 

GTT’s EVP were first introduced in 1968 and it has recently embarked on a major expansion of its operations outside its North American home market. Its Opticom system has already been deployed by more than 3,000 authorities worldwide (including 40 of the top 50 largest cities in the US) covering some 70,000 intersections and 50,000 vehicles. 

The system combines GPS with an encrypted wireless radio to send a signal from an onboard unit directly to the traffic controller as the emergency vehicle approaches the intersection.  Normally it is activated when the driver of the emergency vehicle switches on the lights and/or siren, after which the vehicle continuously transmits its identification, location, heading, speed and turn-signal information on a 2.4GHz channel.

When it comes within range of a signalised and instrumented intersection, the broadcast information is picked up by a receiver on the traffic controller, enabling the system to calculate when the emergency vehicle should arrive at the intersection. The system requests that the traffic controller advances to the green phase in a controlled manner so crossing traffic approaching the intersection is brought to a stop well before the emergency vehicle arrives.

This releases any congestion ahead of the first responder, and the system maintains the green phase until the emergency vehicle has passed.

Beyond saving lives and property, the advantages go wider for many authorities adopting prioritisation systems. “By reducing travel time the service radius of a single station can be expanded, or at least not reduced by increasing traffic congestion,” says Roberts. “If you extrapolate that across the police, fire and ambulance services, it can represent some major savings for authorities by reducing or eliminating the need for new or expanded facilities.”   

Conflict resolution

Should a conflict arise because first responders are approaching an intersection from different directions at the same time, the system will prioritise the vehicles and notify the driver if they will have to stop.  So, for instance, ambulances heading away from the hospital to reach the scene may be prioritised over one returning with a patient who is already receiving medical attention.


Doha

In Doha the Road Maintenance Department of the Public Works Authority (Ashghal) has more than doubled the size of the EVP system in the city and surrounding neighbourhoods, taking the number of intersections in the scheme to 80. An initial 30 installations took place in April 2014 along with the instrumenting of 15 ambulances and 10 civil defence vehicles.

With the latest enlargement fire engines are also being equipped with the system as well as emergency ambulances. Utilising the systems for buses and ministry of interior vehicles may be considered in the future. 
Throughout the process the equipment logs specific data including the vehicle ID, transit time, final green status and other significant event information which is immediately available for retrieval and analysis by dedicated central management system (CMS) software. Similar data is also stored on the vehicle equipment and may be accessed via Wi-Fi networks in the vehicle’s depot/station. As with other EVP suppliers, GTT’s equipment can interface with other ITS systems, report systems and intersection equipment. It can also suppress vehicle identification and associated records where privacy is required.

Updating can be done remotely via the CMS without needing to physically go to each intersection. According to Roberts, an intersection-centric approach means the system is scalable, flexible and enables region-wide coordination while being able to quickly respond to changes in needs such as temporary routes or emergency evacuations.

Transit too

This system of priorities can be extended to provide a Transit Signal Priority (TSP) system which simultaneously supports transit and emergency services. As there are far more buses than ambulances and because timetable adherence is not a matter of life and death, different light sequencing is employed. Unlike EVP where the signal is held on green until the vehicle passes, with TSP an approaching bus will get an advantage by having the green phase be slightly elongated, but it may or may not get through on a single cycle of the lights.

“TSP is one of the only things a bus operator can do to improve service without pushing up operating costs,” says Roberts, adding that payback is typically between 12 – 18 months.

“Unlike emergency situations, with public transit it is not simply a matter of getting to the destination as quickly as possible - there is nothing worse than arriving at a bus stop to see the tail lights of a bus departing ahead of schedule,” says Roberts. This has led to the introduction of the Schedule Adherence and Headway Management options for the TSP system which extend the benefits beyond simply reducing travel times as the system turns TSP on or off as needed to maintain schedule or headway compliance.

For Headway Management the TSP system detects when two buses on the same route are running too closely together and gives priority to the first in order to maintain the gap between buses.

Schedule Adherence and Headway Management can reduce fuel costs and greenhouse gas emissions, while reducing delays and improving the rider’s experience and satisfaction.

Other potential users of the TSP-style system include security services, VIP transport, snow ploughs and so on. High priority vehicles (typically first responders) are always serviced first over the lower priority requests and if the levels are identical, the first request received is serviced first.

 

Emergency preemption technology

	Radio, GPS system	Infrared	Central Green Wave system	RFID systems
Handles non line of slight approaches	Yes	No	Yes	No
Unaffected by environmental conditions	Yes	Yes	No	Yes
Guards against activation of adjacent intersections	Yes	Yes	Yes	Yes
Easily scalable	Yes	Yes	No	No
Does not require preplanned routes	Yes	Yes	No	No
Can accommodate relative priority levels	Yes	Yes	No	No
Logging data sorted at intersection	Yes	Yes	No	No
Logging data stored on the vehicle	Yes	No		No
Adapts activation to traffic conditions	Yes	No		No
Allows simultaneous system activations	Yes	Yes		Yes
Compatible with SCAT/SCOOT	Yes	Yes	Yes	Yes
Incorporates turn signal control of signal phase to be called	Yes	No	No	No
Interoperable with future transit system TSP	Yes	Yes	No	No
Effective range greater than 600m	Yes	Yes	Yes	No