Thursday, March 3, 2011

Traffic Ebb and Flow

We all sit in traffic at some point in the day. We all think that the traffic we sit in is the worst traffic ever. Probably not so, but we are entitled to think it. I am sure that anyone that has sat in traffic has thought, why doesn't the (fill in the blank with governmental entity) fix this.

Well, we are going to try. Not ignoring that you should try other modes of transit to help lessen congestion, the City of Dover has retained a traffic engineer to review our traffic signal management system and an upgrade is underway. We began this project late last summer, and have been working to review the whole system (all 30+ municipally owned traffic lights).

Task 1 – Inventory all 33 signals in the City and upload their existing signal timings into City’s MarcNX (signal management software) system. 11 intersections on upper and lower Central Ave are inventoried, while 7 of those have been downloaded to the MarcNX management software database.

Task 2 – Set-up daily alarms notifications. The consultant has met with departments requiring alarms and is preparing a spreadsheet to implement.

Task 3 – Establish signal system framework and design. An engineered plan for the framework has been developed and is under review. Communications with coordinated systems are systematically being implemented using dedicated phone drops back to the central system, but other methods are being explored to reduce on-going costs.

Task 4 – Address coordination of 7 signals on Upper Central Avenue – Central @ Hannaford’s, Glenwood, Morin, Weeks Lane, Indian Brook, Hotel Drive. Also Indian Brook @ Weeks Lane. Traffic counts have been taken and new timing and coordination plans tailored for four different time/traffic patterns have been developed that coordinate both the east-west and north-south directions at the Weeks signals for the weekday morning, afternoon, mid-day and Saturday peak periods. The consultant created a traffic simulation model in Version 7 of Synchro/SimTraffic to engineer the plans and analyze performance.

NHDOT and the City have agreed to a new maintenance agreement whereby the City will be reimbursed for any work required on state owned signal components of the system. Incompatible signal controllers need to be changed out, and the state DOT has agreed to reimburse the City for approximately 40% of the cost to do so. Somersworth has been contacted by our consultant to inquire if they would allow time-based coordination along the Indian Brook-High corridor to maximize the efficiency.

The consultant intends to conduct field travel time runs “before” and “after” the new programming is deployed to further document actual verses model improvement results.

We don't waste money, so why do this project? What will we get out of it... The most significant benefits that will be realized with the implementation of the initial 2 coordinated signal groups – Central Avenue at Morin, Glenwood, and Hannaford; and Central Avenue at Weeks Lane, Indian Brook, and Hotel Drive, and Indian Brook Drive at Weeks Lane are for the one hour PM commute period, and are as follows:
• Average vehicle delay experienced passing through Weeks Crossing during the PM peak hour will be reduced by 71%
• The number of stops each vehicle will experience during the PM peak hour is expected to be reduced by 31%
• The total fuel savings by all users of this area on a typical weekday during the peak hour will be reduced by 23%, which equates to a total of 60 gallons every weekday or more than 15,000 gallons per year. At $3 per gallon, this equates to a community-wide savings of $45,000 annually.
• CO2 emissions will also be reduced by 23% during this one hour period for a total of annual reduction of 132 metric tons.
• Travel time heading northbound on Central Avenue between Hannaford’s and Hotel Drive will be reduced by 16% from an average of 222 seconds to 187 seconds.
• Travel time heading eastbound on Indian Brook Drive from the Spaulding to Somersworth will be reduced by 81% from an average of nearly 500 seconds to 93 seconds.

Additional Services (Phase 2) – Develop new timing plans for lower Central Avenue Upper Square, Lower Square, and Washington @ Chestnut. The consultant has obtained new turning movement counts from all peak periods and will develop updated timing and coordination plans from these data.

So, what does this all cost (you knew there was a cost here)? $73,492.64.

Anticipated performance improvements associated with the PM proposed timing plan:

Intersection level of service (a measure used by traffic engineers to determine the effectiveness of elements of transportation infrastructure) will be found at the following intersections:
Central at Hannaford’s
Central at Glenwood
Central at Morin
Central at Weeks Lane
Central at Indian Brook Dr.
Central at Hotel
Indian Brook at Weeks Lane

Significant Queue Reductions will be made at:
Glenwood LT. onto Central
Indian Brook EB @ Central
Weeks Lane SB @ Central

Overall network results (all 7 intersections combined)
Ave. Delay/Veh. 243.8 sec 70.4 sec (71% reduct.)
Total Stops 16,461 11,268 (32% reduct.)
Fuel Used 260.3 gal 199.5 gal (23% reduct.)
CO2 Emissions 2.30 tons 1.76 tons (23% reduct.)

Corridor Travel Times
Central Ave. NB 222.1 sec. 187.2 sec. (16% reduct.)
(Hannaford to Hotel)
Indian Brook EB 491.7 sec. 93.4 sec. (81% reduct.)
(Central to Weeks)

Whew, a lot of data to digest, but also a lot of good will be made out of this work. The best part, is that through the training and improvements to computer software and infrastructure, it won't be another 20 years before the timing of these lights are looked at again. Our Community Services staff can review and maintain the lights on an ongoing basis, and make adjustments when necessary to keep things flowing.

So, next time you are stuck in traffic, remember you could be in West Milford New Jersey at the "longest light in America". :)

1 comment:

  1. LOS for cars is one thing, what will be the potential increase (or reduction) in delays for pedestrians, or cyclists that are unable to trigger a given light?

    Presumably this will allow COAST and Wildcat transit to offer faster services, which is great, but all too often these improvements leave bicycles and pedestrians waiting longer than usual.

    A pedestrian, a cyclist and a car driver are all trying to get somewhere, we need to make sure that we do not encourage or enable the car driver to get someplace faster than the pedestrian. A one minute delay for a driver is minimal in a typical commute, but for a pedestrian it can be a significant loss of time. Not to mention the risk that if pedestrians are required to wait longer, they will decide to cross against the light and potentially be involved in a crash.

    I welcome the efficiency upgrades, for sure, its a great use of funds, but lets make sure other road users (individual pedestrians and cyclists) are not left out in the cold, to allow individual drivers faster commutes.