Building an open standard for emergency vehicles from the ground up

Commentary: Unsatisfied with the limitations of traditional emergency vehicle preemption systems, a project manager with the City of Redlands, California, explains how staff are building a new modern standard.

Get the basics of public safety infrastructure wrong, and disaster may strike twice — once when an emergency hits, and again because of a delayed response. Nowhere is this truer than for the systems that get first responders to the scene of an incident.

Estimates suggest a 10 percent reduction in cardiac arrest survival rates for every extra minute of response time. After five minutes, only 50 percent of victims live. After 10 minutes, very few survive. Clearly, getting first responders on-site as fast as possible has real life/death implications.

Unfortunately, it’s incredibly expensive to put a fire station at every street corner. The unpredictability of traffic exacerbates the problem. We all know that traffic congestion imposes economic costs on drivers, but most of us probably aren’t thinking about lives lost to congestion. One evolving solution comes in the form of technology that allows emergency vehicles to request priority green lights at upcoming intersections along their route. Known as emergency vehicle preemption (EVP), such systems are typically built around proprietary hardware with little or no interoperability between vendors. The City of Redlands, California, is planning an open-standard EVP system that will eliminate many limitations of traditional designs.

Around since at least the 1960s, EVP is relatively simple in concept but difficult to implement in the real world. There are lots of ways to make signal preemption work. Early solutions used microphones to detect the sound of a siren. More advanced systems rely on infrared light or GPS radios to communicate with intersections. All of these systems struggle with vehicle speed, direction of approach and hacking or other abuse. Even the most advanced modern GPS triggers lack sufficient range and don’t integrate well with dispatch systems.


A few companies are experimenting with what they’re calling preemption servers. These are back-end systems that track vehicles dynamically and activate signals with more lead time. Such systems, however, are still relatively expensive to deploy because they rely on proprietary communication hardware and specialized software.

An ideal solution would instead take advantage of existing on-board computer equipment and standardized back-end systems that many cities already support. This would reduce the need to buy extra equipment and dramatically cut costs.

The fundamental problem, and the reason a typical EVP system is built using proprietary hardware, is the outdated state of traffic controllers. Most controllers require the use of a piggyback device that essentially overrides the controller during a preemption event. All that duplicate hardware is prohibitively expensive — several thousand dollars per intersection, not to mention the cost of equipping each truck and the expense of running a back-end server system.

Collaborating with several partners in the industry as well as other interested agencies, staff at Redlands are working to deploy a software-based EVP routing system that leverages existing vehicle location equipment and communicates with upcoming intersections via DSRC radios and cellular cards simultaneously. When complete, this approach will be easily and cost effectively replicated anywhere in the world with only minor modifications to adjust for local traffic engineering standards.

Eventually, this entire mechanism will be built into the underlying hardware that already exists on firetrucks, police cars and traffic signals and will leverage standard GIS software to manage location data and vehicle routing. This will dramatically reduce the cost of implementing EVP capabilities and allow for a host of advanced solutions such as event specific routing, congestion awareness and vehicle-to-vehicle alerting (critical for EVP to function in an autonomous vehicle world). While early concepts are showing promise, there are a few aspects that require more work. Redlands expects to have a prototype running later this year. 


If you’re interested in learning more or getting your city involved in development, reach out to Project Manager Kjeld Lindsted via LinkedIn for details.

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