EVP — What Are The Benefits?
EVP systems are designed to give emergency response vehicles a green light on their approach to a signalized intersection while providing a red light to conflicting approaches. The most commonly reported benefits of using EVP include improved response time, improved safety, and cost savings. These benefits have been realized since the early deployments of EVP and have been documented since the 1970s. Selected key findings are summarized here. Later in this report, these findings are echoed by the jurisdictions that are visited as part of the EVP study.
Improved Response Time
EVP can improve EV response times by reducing the probability that responding EVs will arrive at intersections during the red signal phase and encounter significant queues. In highly congested areas, EVs may encounter extended queues that force them to slow to a crawl, adding seconds or minutes to the time required to reach the scene of an incident. A green light gets the queue moving and the traffic dispersed before the EV arrival allowing the EV to maintain higher average speeds than would be expected given intersection spacing along the route and normal traffic conditions.
In 1978, the City of Denver Department of Safety produced a study2 reporting changes in EV response times as a result of signal preemption. The study was conducted over a 90-day period in an area involving three fire stations and 75 signalized intersections. Firefighters recorded travel times necessary to traverse typical routes before and after preemption installation. The data showed EV response times decreased by 14 to 23 percent, with savings of approximately 70 seconds per response on a route with three to six signalized intersections.
Improved Safety and Reduced Liability
EVP can reduce the chance of an EV crash at a signalized intersection. Nationwide, over the past 10 years, more than 25 percent of all EV crashes have been found to occur at signalized intersections.3 These crashes often involve situations where vehicles approaching a green signal cannot see an EV approaching on the intersecting roadway because of line-of-sight problems with nearby buildings, vegetation, or hills. For these situations, EVP provides familiar guidance to private vehicles by showing a red signal at the conflicting approaches, thereby bringing these vehicles to an orderly stop. Safety benefits can be measured by comparing EV crash histories or, as a surrogate, by measuring the reduction in number of and severity of conflict points that may be present at the time when an EV traverses the intersection.4 A decrease in EV crashes reduces public liability associated with fatalities, injuries, and property damage. Over the past 10 years, there have been approximately 80 EV crashes each year in the U.S. that involve fatalities.5
In 1977, at the request of city officials, St. Paul's fire chief conducted a pre-and post-EVP safety impact analysis.6 The fire chief studied EV crashes before and after the EVP system deployment, and reported on the preemption deployment rate and the crash histories. Over the period from 1967 through 1976, the City of St. Paul deployed preemption on 285 of 308 intersections. During this period, the number of EV crashes decreased from the 1967 high of eight to an average of 3.3 per year in the latter years of the study.
Cost Savings in Fire/Rescue and EMS Planning
As EVP systems have the potential to improve response times and safety, this trend can translate into cost savings for the community. Response times for fire/rescue and emergency medical services are important measures of effectiveness for local public safety departments and are key elements in fire/rescue and emergency medical service planning. In defining service needs, jurisdictions consider fire flashover7 times (Figure 1) and survival rates for cardiac patients (Table 1) along with a study of local conditions, including development density and loss potential. ITS solutions, such as EVP, can lead to improved EV response times increasing the effective service radius of a single station.
Figure 1. Generalized Flashover Curve for Residential Construction8
| Time Until Defibrillation | Survival Chances |
|---|---|
| With every minute... | Chances are reduced by 7-10% |
| After 8 minutes... | Little chance of survival |
| Blacksburg, Virginia was able to raise its ISO Class, reflecting the response time improvements made possible by EVP deployment. |
For example, Loudoun County, Virginia is one of America's fastest growing counties.10 As such, the county evaluates its current and future fire/rescue and emergency medical service plans given the county's rapid transition from a rural area to a mixed-use area. The influx of new population centers and the increase in congestion on arterial roadways challenge the county. In a January 2003 study,11 the county examined future fire/rescue and emergency medical service plans identifying the parameters to be considered in selecting the number of stations, the location of the stations, and the required number and type of apparatus that will be required. One of the key considerations in the planning process is average EV operating speed and the effective service radius given response time goals.
Cost Savings on Fire Insurance Premiums
Improved response times can lead to an improvement in the insurance industry ratings of a community's fire suppression service, with a corresponding reduction in fire insurance rates for residential and commercial property owners. The Insurance Services Office (ISO), through its Public Protection Classification (PPC) program, assigns insurance ratings to each participating community once every 10 years.12 By classifying a community's ability to suppress fires, the ISO helps the communities evaluate their public fire protection services and plan improvements. The ratings are very important to communities as they pursue growth and economic development plans. Some communities, such as the Town of Blacksburg, Virginia have reported that its ISO Class had been raised reflecting the response time improvements made possible by EVP deployments.13
2 City of Denver Department of Safety (1978). Time Study on the Effectiveness of the Opticom Traffic Control System (Year 1978), report prepared for the City of Denver by the Denver Department of Safety, FHWA Report No. D-ORTS/78.5.
3 U.S. DOT (2003). Fatality Analysis Reporting System (FARS) Web-Based Encyclopedia Queries for Emergency Use Crash Statistics. http://www-fars.nhtsa.dot.gov.
4 Louisell, William C., Collura, John, and Tignor, Samuel C. (January 2003). Proposed Method to Evaluate Emergency Vehicle Preemption and Impacts on Safety, Paper presented at the 82nd Annual Meeting of the Transportation Research Board, Washington, D.C.
5 U.S. DOT (2003). Fatality Analysis Reporting System (FARS) Web-Based Encyclopedia Queries for Emergency Use Crash Statistics. http://www-fars.nhtsa.dot.gov.
6 Fire Chief, Department of Fire and Safety Services, St. Paul, Minnesota, Emergency Vehicle Accident Study (Year 1977), a letter written from the Fire Chief to a City Councilman, 1977.
7 The National Fire Protection Association Handbook defines "flashover" as the point when "all combustibles in the space have been heated to their ignition temperature and spontaneous combustion occurs."
8 National Fire Protection Association (2001). NFPA 1710 - Standard for the Organization and Deployment of Fire Suppression Operations, Emergency Medical Operations, and Special Operations to the Public by Career Fire Departments.
9 American Heart Association Website (2004). http://www.americanheart.org.
10 U.S. Census Bureau Website (2004). http://www.census.gov.
11 Loudoun County Public Safety Service Planning (2003), EMSSTAR Final Service Plan. http://www.loudoun.gov/fire/index.html.
12 Insurance Services Office Website (2004). http://www.isomitigation.com
13 Town of Blacksburg, Virginia (2000). Annual Report for the Year 2000.