Lessons Learned
This section summarizes the lessons learned reported by the three sites so that those considering EVP can minimize deployment delays and maximize system performance. The lessons presented were common across the three sites. They are presented in terms of institutional issues, public acceptance, EV driver training, system installation, and system maintenance.
Overcoming Institutional Issues
- Involve all appropriate stakeholders in a collaborative manner throughout the planning, deployment, and operations phases. EVP systems have the capacity to impact a number of city, county, and state agencies. Successful EVP projects will involve a wide-ranging stakeholder group that should consider a memorandum of understanding outlining the short and long-term roles of each member.
- Identify a champion and define the role to maintain a consistent advocacy message. To prevent the effort from stalling, it may prove beneficial for the stakeholder group to designate a specific champion for the system. In a typical EVP deployment, the initial champions come from the fire/rescue and EMS community. Over time, however, local officials become advocates, or maybe even champions, as local governments decide whether or not to support the system financially.
Public Acceptance
- Launch a public awareness campaign highlighting the public safety benefits of preemption at these and other signals. An important step in achieving public acceptance is to inform the community of the purpose and benefits of EVP. Extra outreach may be needed in areas surrounding intersections near hospitals or fire/rescue and EMS stations as these intersections experience more preemption calls than other intersections, often resulting in more delays around these facilities.
EV Driver Training
- Document standard operating procedures and driving techniques and review them in regular training sessions. Driver training is key to minimizing EV crashes. EV drivers at each site visited stated that the main lesson learned was not to over-rely on the system and to proceed as if preemption would not be granted.
System Installation
- Bench test the equipment and software in the shop with the same equipment that is found in the field. Bench testing prevents potential problems in the field. VDOT found that traffic signal controller software required an upgrade to allow dual use of the technology for both EVP and transit signal priority. Prior to the upgrade, testing revealed that transit priority requests would be granted the same level of precedence as EVP requests, whereas VDOT wanted EVP requests to take precedence.
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"In nearly every situation, some type of adjustment was needed to clear the way for using preemption and priority...it was not a purely 'plug and play' application." — Bob Sheehan Signal Systems Manager VDOT |
- Wire the vehicle emitter into the EV parking brake or transmission lever to turn the emitter off while the EV is stopped. When EVs stop in the vicinity of an intersection, a continuously running emitter will hold the signal in the preemption phase indefinitely, causing significant traffic problems. Systems with factory-installed emitters are usually delivered with a power interrupt tied to the transmission shift lever that disables the emitter when the vehicle is in "park." Both the Fairfax County and Plano apparatus shops had to develop custom power interrupt solutions for vehicles with locally-installed emitters.
- Maintain an open line of communication among stakeholders during the acceptance testing period to avoid poor system performance and perhaps avert a dangerous situation. Resolving system performance issues requires cooperation and communication between EV drivers and EVP maintenance technicians. Certain signalized intersections may pose problems in terms of emitterdetector line-of-sight reducing detection ranges. Finding the right solution requires detailed problem descriptions.
System Maintenance
The key to maintenance success is identification of a single agency to be responsible for scheduling, coordinating, and funding system maintenance. This agency may be the city traffic engineering department or the fire/rescue and EMS department. If the fire/rescue and EMS department contracts out for maintenance services, a memorandum of agreement should be drafted with the agency that controls signal cabinet access to document service call precedence, cabinet access procedures, service log requirements, and any other necessary site-specific coordination issues.
- Develop a maintenance problem-reporting channel. The purpose is to enable the users of the system to easily report problems so that problems can be screened for response priority and the potential for dangerous situations is minimized. Figure 10 shows a VDOT technician in Fairfax County, Virginia overseeing contract maintenance on the EVP system.
- Ensure a standard fault isolation protocol is in place. Having a documented system for trouble-shooting will reduce the repeat/recur rate as well as the maintenance call false alarm rate.
- Perform concurrent maintenance. In addition to serving maintenance requests, there may be benefit in performing preventive maintenance in conjunction with regular traffic signal equipment maintenance. A task such as detector lens condition inspection can be done in conjunction with signal lamp replacement. St. Paul reports that this practice has helped reduce service calls.
