EVPs, or Emergency Vehicle Preemption, are small strobe lights placed on top of traffic signals. The EVPs installed in Tucson are called Opticoms, which have a bright flashing strobe light emitted when a first responder vehicle approaches. It is a system aimed at preventing civilian collisions with first responders by changing the traffic light in the flow of traffic for the first responder vehicle.
Proposition 411, nicknamed “Tucson Delivers: Better Streets Safe Streets” was a question on the 2022 midterm election ballot, aimed at improving street safety in Tucson.
It extended the half-cent sales tax for 10 years starting in 2022. It’s expected to raise $740 million, with 20% of that going to improving road safety with “traffic signal technology upgrades, and traffic-calming features.” The Tucson Department of Transportation confirmed that the EVPs are one of the many technological advancements installed at the intersections with this proposition. However, only some of the EVPs have been updated with this funding.
According to the Tucson Department of Transportation 313 of the 407 signalized intersections in Tucson are equipped with preemption equipment made by TOMAR Electronics Inc.
Opticoms have an optical receiver, about the size of shot glass, and a confirmation light, similar to a ping pong ball. When a first responder vehicle turns on its sirens, there is a small strobe on top of the vehicle that triggers the confirmation lights at that intersection.
Tom Paul, a retired Deputy Chief with Tucson Fire Department, explained that the confirmation lights are to specifically notify the particular first responder vehicle as they are accelerating.
“So in our trucks there is a strobe light that is mounted on the top of the truck and when you turn on your emergency lights that strobe light turns on,” said Paul. He explained that there is a specific frequency that trips the EVPs and changes the traffic light from red to green.
The Tucson Department of Transportation confirmed that some of the intersections with EVPs have an optical detection sensor that looks like a camera. However, the purpose of this device is to monitor traffic flow and does not record anything. The optical sensor cameras aren’t even connected to the EVP systems.
When the confirmation lights of the EVP flash the traffic light will turn green, this lets the firefighter know that the Opticom has detected its siren and can approach the intersection when heading to a call.
But sometimes the EVP does not work, and Paul remembers before retiring five years ago that instances would cause confusion at an intersection.
“It does come at an expense, it costs money to keep those things functioning. And they do malfunction every once and awhile,” said Paul.
In Tucson, specific intersections have EVPs that only detect first responder vehicles from a particular department.
On Sunday Dec. 7 at 3:59 PM a AMR ambulance was heading westbound on a call with its sirens and warning lights on. A car heading south on Cambell struck the ambulance. The EVPs on the intersection of Campbell and Speedway did not go off.
No amount of money from prop 411 could have prevented a collision with a vehicle not equipped with Opticom for that intersection.
According to the Tucson Department of Transportation this intersection has EVPs only detected for Tucson Fire Department vehicles that are in a Code III situation. The ambulance involved in the accident was with a private company and not through the Tucson Fire Department. Not all first responder vehicles are equipped with the Opticom system. Also, not all calls warrant the use of EVPs, according to the Tucson Department of Transportation.
An officer at the Tucson Police Department confirmed that none of their patrol cars are equipped with the Opticom system, like they are in other U.S. cities. This is designed for a specific reason.
The Tucson Fire Department added that they do not support police cars or private ambulances to be equipped with Opticom as it would be competing for right-of-way passage especially near trauma centers.
The main reason EVPs only detect Tucson Fire Department vehicles at populated intersections, like the ones on Campbell and Speedway, is to avoid having two departments going to a call and arriving at the same intersection at the same time. The Opticom system is designed to not override the first time the EVP is tripped, and will never change green for opposite directions.
However, there is hope for more intersections to have EVPs with the $30 million technological upgrades in Proposition 411.
“If you are on another truck and you know you are going to a call with other units you see the Opticom changing but it is red in your direction, you’re thinking ‘okay, there is another person or truck coming from another direction,’” said Paul.
Collisions with first responders do happen, but as Paul explained, it is not the fault of the EVP if it does not function properly. Sometimes a person waiting at an intersection is aware of a first responder next to them, but does not see the traffic light change color. This can cause an accident and force the fire truck to miss their intended call.
As the Tucson Department of Transportation stressed, these EVPs are supplemental devices, not required by federal law. Is it the civilian’s responsibility to yield for a first responder or stop their vehicle, regardless if an EVP system is in place.
Proposition 411 is aimed at making these incidents less dangerous one intersection at a time. Major construction started in 2024 and is 31.7% complete as of Dec. 2025. The first stage is expected to be complete by 2029.
