In the fall of 2008, the New York City Department of Transportation (NYCDOT) embarked on a program to ease traffic congestion, improve air quality, discourage speeding and increase pedestrian artery cross-time and safety through a method of signal retiming that did not rely on massive data collection or extensive computer modeling to meet these goals. Corridor greenbands, which are the amount of time a band of traffic receives a green traffic signal, were created to improve vehicle platoons, hinder speeding, and return excess phase-time back to the side-street and pedestrian crossings. With large improvements to traffic signal infrastructure in the last decade, today’s centralized traffic signal control system can communicate, implement and monitor numerous signalized intersections’ timing plans and readily allow localized signal timing based on time-of-day/day-of-week, traffic response and/or adaptive control requirements. With this newfound ability, NYCDOT set out to overcome and improve upon the basic pre-timed signal settings that plagued many City areas; the challenge was to do it at a large scale and cost effectively.
With the technology infrastructure in place, the design team embarked on the retiming methodology using low cost marketplace software to optimize timing plans, which quickly expanded to eight phases that encompassed 63 corridors and 2650 intersections throughout the five boroughs of NYC. Analyses indicated the traffic signal timing actually provided an average improvement in travel speed along the routes of 2.1 miles per hour that ultimately translated over 365-days into:
- 8,300,000 vehicle-hours of time saved from delay reductions each year
- 7,650,000 gallons of fuel saved each year, 12.2 % savings
- Reduction in harmful airborne environmental emissions each year:
- 275,000-lbs less Volatile Organic Compounds (VOC)
- 225,000-lbs less Nitrogen Oxides (NOx)
- 1,200,000-lbs less Carbon Monoxide (CO)
- The monetary benefits were $120-million resulting in a benefit cost ratio of 40-to-1.
But what is really innovative and unique in this NYC project is the initiative to improve pedestrian safety along with congestion, which are often opposing aspects of the timing module. Further, Mayor DeBlasio’s “Vision Zero” initiative was adopted with the goal to eliminate all pedestrian accidents. As such, this NYCDOT timing initiative became a cornerstone in reducing vehicle speeds to 25 MPH through the modified timing plans of this program. Therefore, unlike other hard improvements, these timing plans are sustainable as they can be simply modified to accommodate new directives, volume adjustments, or new area developments, which have proven to be extremely cost-effective.
By implementing this traffic signal timing program, the City has created a procedure that will service their needs today and well into the future. The public will realize the real benefits of this system as the improved travel times translate into less time on the roads, improved air quality, less spent on energy and an improved quality of life and safety for pedestrians. This project demonstrated that with proper planning, design, coordination and implementation, we can manage our roadways and concurrently achieve congestion mitigation, reduction in vehicle delays and fuel consumption, improvements to air quality, and most important, general safety for all.