Harnessing vehicle GPS data, the system offers a cost-efficient alternative to conventional timed signals
A new traffic signal timing system that uses vehicle GPS data to significantly reduce the number of stops at intersections is rolling out in a trial in Oakland County and could eventually be expanded across Southeast Michigan.
The system, developed by University of Michigan engineers, needs GPS data from as little as 5% of vehicles on the road to recalibrate signals every few weeks, preventing unnecessary stops.
In partnership with the Road Commission for Oakland County, 13 signaled intersections have been updated so far with U-M's system:
- Four signals along 8 Mile Road, from Orchard Lake to Brentwood Street in Farmington Hills, resulting in a 30% reduction in delays and a 40% reduction in stops over that stretch.
- Nine signals along 12 Mile Road, from Vinsetta Boulevard to North Connecticut Avenue in Royal Oak, resulting in a 20% reduction in both delays and stops.
In the next six months, as many as 40 intersections will be equipped with U-M's technology, which is being prepared for commercialization by the new startup Connected Traffic Intelligence. These improvements are made possible by a $1.4 million grant from the U.S. Department of Transportation.
There are roughly 320,000 traffic signals in the United States and the annual congestion costs-direct and indirect-associated with those intersections comes out to $22.9 billion. Those costs include time spent waiting at lights as well as unnecessary energy consumption caused by poor signal timing.
"We utilized the GPS data to scan over 1,400 intersections in Oakland County and identify the 30-40 intersections that would most benefit from our retiming updates," said Zachary Jerome, a postdoctoral research fellow at U-M's Transportation Research Institute. "Vehicle telematics data provides us with opportunities that were previously unavailable to evaluate traffic signal timing performance across entire traffic networks. It enables us to proactively pinpoint inefficiencies rather than having to install roadside detection systems at every intersection."
U-M's technology uses data from about 6%-10% of all vehicles on the road in the U.S., with GPS data standing in for traffic detection at an intersection. For example, a tracked vehicle that comes to a stop roughly 100 feet from an intersection strongly indicates that it is behind at least three or four other vehicles. Over an 18-month period beginning in 2023, U-M's system was in use at 34 intersections in Birmingham, Michigan, producing a 20%-30% decrease in stops. And while it will benefit motorists tired of sitting at red lights, road commission officials believe it will help improve safety as well.
"This will help us identify intersections where there is congestion and delay," said Danielle Deneau, director of the traffic safety department at the Road Commission for Oakland County. "We can correlate or compare that to intersections where there are high frequencies of crashes. With that in hand, we can make improvements on the timing of those traffic lights that will hopefully reduce the number of crashes."
Most traffic signals operate on a time-of-day signal timing plan, where preset patterns are in place morning, afternoon, evening and overnight. Traffic planners attempt to coordinate those cycles with surrounding intersections to allow cars to flow between intersections with as little stop-and-go travel as possible.
Optimizing signals to keep up with changes in traffic flows isn't a simple task. The time and cost of traffic counts and recalculation, taking roughly two to six months and up to $4,500 per intersection, mean most municipalities won't reassess for two to five years and sometimes even decades.
While adaptive signals have been around since the 1970s, the cost of detecting vehicles at intersections and reprogramming signals in real time, as much as $50,000 per intersection for installation alone, has limited their use. Oakland County began using adaptive traffic signals in the early 1990s. Today, roughly 850 of the county's 1,500 total signals are adaptive. U-M's system could significantly improve timed lights for a much lower price, an estimated $2,500 per intersection per year.
"As our system does not rely on infrastructure-based sensors, it is very scalable and can be implemented for the entire Southeast Michigan so that more drivers can save travel times with lower signal retiming cost," said Henry Liu, director of UMTRI and a professor of civil and environmental engineering.
Funding from USDOT comes through the Strengthening Mobility and Revolutionizing Transportation program, which supports "advanced smart community technologies and systems in order to improve transportation efficiency and safety."
Connected Traffic Intelligence has licensed the technology and a patent application has been accepted. Liu, Jerome and the University of Michigan have a financial interest in Connected Traffic Intelligence.
