Main Street Traffic Studies: 8000+ Vehicles a Day

A pair of recent traffic studies of lower Main Street in New Canaan found that more than 8,000 vehicles a day were traveling this collector road – a road which is a primary route for emergency vehicles, as well as emergency evacuation.  The studies were conducted of northbound and southbound traffic at Woodland Road during the short July 4th holiday week. Some of the studies’ conclusions need to be adjusted, since they assume a speed limt of 25 mph; the posted speed limit there is 30 mph.

The number and type of vehicles and their speed was recorded in 60 minute time periods, from 12 AM on 7/01/08 to 12 AM on 7/03/08, lasting a total of 48 hours. For northbound traffic, the AADT (average annual daily traffic) Count was 4,088. For southbound traffic, the AADT Count was 4,423. The total AADT Count for both lanes is 8,506.  It is reasonable to assume that these numbers would be higher during the school year, when more famliies are in town (a more accurate AADT would take into account such season variations). One would also expect the detailed breakout numbers shown during rush hours and school opening/closing times to be higher during the school year. 

Most of the vehicles were passenger cars; 211 were small trucks, 45 were large trucks or buses, and 15 were tractor trailers. (The study was conducted prior to the beginning of the Mill Pond drainage project.)

The mode speed in both directions was 30 mph; at least half of the vehicles were traveling at a speed of 30-34 mph or lower. Northbound the average speed was 32, and the 85th percentile speed was 39.57 mph. Southbound the average speed was 31, and the 85th percentile speed was 36.48 mph.

What is also interesting is the number of vehicles traveling in excess of 55 mph: 104 (2.74%) northbound and 58 (1.38%) southbound. Multiply that by 365 days a year. And this is in one of several sections of lower Main Street that are already “narrow” by the “traffic calming” goal of the proposed construction: 24 feet.  Also revealing is that these speeding vehicles are most likely to be found during morning and afternoon rush hours, not in the wee hours of the morning as one might suppose.

Would you like to be walking on a sidewalk right next to a 55 mph vehicle? A loud dump truck or a tractor trailer splashing mud? There’s not room for a buffer between the proposed sidewalks and this heavily-traveled road. And when there’s a sidewalk on only one side, walkers tend to cross the road to get to it, often jaywalking and surprising drivers.

Here are the studies for those of you who would like more detail (remember that the speed limit is 30 mph at this point on Main Street, not 25 as the studies say, so the conclusions about the number of speeding vehicles is incorrect.)

• Northbound Main Street at Woodland Road, 12 AM 7/01/08 – 12 AM 7/03/08
  
• Southbound Main Street at Woodland Road, 12 AM 7/01/08 – 12 AM 7/03/08
  

Narrowing Main Street to Make Room for Sidewalks

Residents of Main Street were surprised and disturbed to learn that the lanes will be narrowed to 11-12 feet to make room for the new sidewalks that have been proposed.  The narrowing is described as a “traffic calming” measure that will reduce speed. A representative of New Canaan’s police department notes that narrowing the lanes on Main Street should result in a 3 mph speed reduction.

Traffic Calming in New Canaan

According to the Police Commission Traffic Calming description on the Town’s website, “Traffic Calming measures are not to inappropriately delay emergency response to fires, medical or other emergencies. Certain streets and roads have been identified as emergency response routes where certain traffic calming devices that increase response times will not be considered.” Main Street is identified as an emergency response “collector road.” With narrow lanes bounded by curbed sidewalks, we wonder where other vehicles will be able to pull over when emergency response vehicles need to pass.

“Traffic calming must be neighborhood driven and it is necessary to keep residents informed,” the Police Commission site continues. “Residents of an area identified as possible installation sites must be given the opportunity to participate in the discussions leading to the implementation of such proposals.” Many residents of lower Main Street, who have observed the traffic patterns for years, have expressed their concern about the wisdom of narrowing this winding, hilly, heavily traveled road.

SWRPA – A Regional Study

In the late 1990’s the eight communities in Southwestern Connecticut commissioned a study of traffic calming measures.  A paper describing this SWRPA traffic calming project notes that “Roadway classification was found to be critical. Studies on most traffic calming devices have recommended that such devices are not appropriate on arterials and should be of limited use on collectors.” The full study, A Traffic Calming Toolbox, is available at the New Canaan Police Station.

ITE – Industry Standards

According to the Police Commission, “Traffic calming measures shall be designed to comply with recognized standards and practices of the Institute of Transportation Engineers, ASHET and the Connecticut Department of Transportation.” In 1999 the ITE published “Traffic Calming State of the Practice,” which found “minor” speed reduction for street narrowing.  The sample size of 7 road narrowings produced an average speed reduction of 2.6 mph, with a standard deviation of 5.5 (page 104). What does this mean? There’s not a strong correlation between street width reduction and speed. 

Most of the published studies on traffic calming have a large margin of error, offering weak confidence in the predictive value of their conclusions.

In fact, most of the available studies on street narrowing are documenting projects where the streets are straight and flat, often in towns where roads are laid out in a grid. Main Street is none of these. Narrowing is often accomplished by permitting on-street parking, or by drawing the outside lane lines closer to the center lane.

Among the disruptive trade-offs:

• Emergency response vehicles are delayed,
• Trucks, school buses and other large vehicles have a more difficult time navigating the roadway,
• Traffic impacts are shifted to other roads, and volume increases on side streets.

We question whether narrowing Main Street is wise. If the stated purpose is to lower the speed, why not start by reducing the speed limit?

Or are we about to build a permanently dangerous change into our Town’s infrastructure, inconvenience drivers, and slow passage of emergency vehicles in order to accommodate sidewalks?