Benefits of Florida's traffic signal retiming

Lee County in Florida has consolidated dramatic results of a major traffic signal retiming with installation of advanced monitoring and management technology for generating further benefits. 

The 6841 Lee County Department of Transportation (DOT), in the US State of Florida, has completed retiming of traffic signals for over 50 intersections in the cities of Fort Myers and Bonita Springs. The project aimed to evaluate existing operations and enable adjustments to optimise flows, and has produced dramatic results.
 
The DOT calculates the overall cumulative project benefits as a 23% annual reduction in travel delays equating to US$15,300,000 in value of time saved; 21,200 litres of fuel saved per day equating to US$2,000,000 per year; and a 19% reduction in emissions representing an annual benefit of US$124,000.

Florida Department of Transport funding of US$357,400 covered the cost of engineering consultancy to devise new timing plans for county staff to review. Lee County Chief traffic engineer Stephen Jansen told ITS International: “The large benefit to cost ratio comes from a lot of drivers experiencing small improvements.

“For the most part, reductions in travel time were only a few seconds per intersection per vehicle, but there are thousands of drivers per day on these roads so the benefits add up quickly. Overall, they are being maintained and occasionally exceeded.”
The project was phased to allow relevant data collection for the February-April 2011 peak and July-September 2011 off-peak traffic seasons. (The area has a large influx of seasonal winter residents).

Determined in real-time

In its most recent initiative, the county has leveraged the Travel Time module of 1763 Econolite’s Centracs centralised advanced transportation management system, which it installed in 2011 as part of the project. This has enabled deployment of a 826 TrafficCast BlueTOAD (Bluetooth Travel-time Origination And Destination) sensor array to detect anonymous Bluetooth signals broadcast from mobile devices to determine travel times and speeds in real-time.

The Centracs database stores travel time and speed information collected from the TrafficCast servers to allow comparison of travel time and speed performance over different time ranges. The system can also use BlueTOAD speed thresholds to trigger alerts and actions. 
Lee County signal retiming

Cost:
US$357,400

Benefits:
$15,300,00 in time savings

$2,000,000 in fuel savings

$124,000 reduction in emissions
Says Jansen: “Because of Centracs’ modular design, we’ve been able cost effectively to expand our capabilities as funding permits. In this case, the integrated module has enabled us to immediately manage and control our BlueTOAD system without the hassle and extra costs associated with purchasing additional equipment and software. The system fits well with our long-term plans to optimise traffic flows and safety along major arterials, such as US 41.” The county is currently installing a fibre-optic communications network and expects half of its signals to be linked by early 2013.
Informed decisions

Jansen sees monitoring via the new Travel Time module and BlueTOAD interface as allowing the motoring public to gain real-time information on traffic congestion and so make informed decisions on their trips, resulting in less overall delay, reduced travel time and reduced pollution emissions. He expects to have a public interface working by the end of 2013.

Real-time monitoring allows the DOT’s operations centre to identify incidents that may require revised signal timing. For example, if a southbound lane of a freeway is closed, forcing travellers onto alternative streets, a special signal plan can give more green time to exit ramps to clear traffic.

“This results in less congestion around freeway interchanges, reduced travel times and emissions, and fewer secondary crashes. Not least, long-term travel time monitoring can help identify where we may need to allocate resources to retime signal systems or build new capacity,” Jansen says. “The rule-of-thumb is to retime a system every three years, however, some systems are very stable and do not need retiming while others are more volatile and need retiming more often. With long-term monitoring we can identify trends and be more efficient in assigning resources”.