Focus On - Princeton

As promised, the next installment in WalkBikeJersey’s “Focus On” special is of Princeton. To be more specific we will be focusing on Princeton Borough and in particular one neighborhood in close proximity to downtown.

The reason why I choose Princeton Borough for the second installment was due to some of the innovative and rare traffic calming features (at least in New Jersey) found in the neighborhood just to the southwest of downtown. This neighborhood is bounded by Stockton Street and Bayard Lane (Route 206), and by Great and Westcott Roads and contains some of the finest homes in all of New Jersey, which undoubtedly means that it also has some of its most wealthy residents. While there are only residential land uses in this neighborhood, nearly all the streets connect through to the other main thoroughfares leading in and out of this side of town. During rush hour, traffic backs up rather badly at the intersection where Route 206 meets the terminus of Route 27 (Nassau St). As such this neighborhood is subject to drivers looking to circumvent this congested intersection, particularly those traveling through town on Route 206.


View Princeton - Traffic Calmed Neigborhood in a larger map

To mitigate drivers speeding through the neighborhood about ten years ago Princeton Borough installed a number of advanced traffic calming devices. You won’t find a single primitive speedbump here! Instead borough officials used a coordinated ensemble of different devices such as mid-block neck-downs, mini traffic circles and low, cobbled traffic islands. Through connections on one or two streets have also been closed to motor vehicle traffic but the sidewalks have remained to allow bicyclists and pedestrians continued, convenient access. Overall, the application of all these traffic devices was refreshingly sophisticated and novel which is appropriate for a community with one of the greatest brain trusts in Western Civilization.

The most common traffic calming device used in the neighborhood were traffic islands located in the center of the streets, usually just in front or behind an intersection depending on ones approach. The islands are made with low lying Belgian block that is only an inch or two higher than the asphalt at the margins but then rises a few inches more near the center. The design details of this feature causes enough discomfort to discourage drivers of passenger cars from riding over them, therefore requiring them to slow down to avoid the islands, but will not cause any damage to a car if they do. However these traffic islands are easily driven over by large trucks or emergency vehicles like fire engines, on the rare occasions these vehicles must traverse these streets to reach a local destination.

This photo demonstrates some of the construction details common
to all of the traffic calming islands in this neighborhood.
The first set of Belgian blocks is about an inch above the grade of the asphalt
and the islands are crowned at the center about three or four inches more.

Neck-downs or a narrowing of the street on both sides are also used in several key locations. From what I observed, these neck-downs move the curb in towards the centerline of the roadway less than the width of a parallel-parked automobile but they still leave enough room for two oncoming cars to pass one another inside the device. In one location a neck-down not only slows traffic but also provides room for a sidewalk while eliminating to need to take down a large specimen tree that happened to be close to the street. Very clever!

This neck-down narrows the street about two feet on either side.
It would appear that the neck-down provided enough space to place a sidewalk on the
right side of the street without calling for the removal of the large trees in the background.

Finally, the most unique traffic calming device were mini traffic circles used at two, four-way intersection. While routinely used in the Pacific Northwest, particularly in Portland, this is the only application of this device that I have observed in New Jersey. Mini traffic circles are placed in the center of a four-way intersection usually without modifying the dimensions of the curbline at the corners. They are about eight to twelve feet in diameter and are typically landscaped with ornamental vegetation, often including a tree as was done at the two intersections in Princeton. Stop signs are replaced with yield signs and drivers are expected to yield to traffic already in the mini-circle, as is typically the custom, and proceed around the circle to the right in a counterclockwise direction.

This mini-circle is located at the intersection of Lafayette Road and Cleveland Lane.
Notice the various signage, crosswalks and the mini-circle itself with landscaping including tree.
Also notice how the landscaping could block a drivers view of pedestrians in the far crosswalk.

The original idea behind this device was to force drivers to slow down and drive with caution through the intersection, particularly those who are driving straight through the intersection and who may not have had a stop sign prior to the installation of the mini-circle. On the flip side, replacing stops signs with yield signs after installation of the mini-circle also allows for freer movement of traffic, eliminating unnecessary (and energy wasting) complete stops and replacing them with slow, cautious yields. Being able to cautiously and safely roll through an intersection can be especially beneficial to cyclists who like to maintain their hard earned momentum. Also, the additional greenspace and landscaping does add extra beauty to the neighborhood and at around 10 feet in diameter, the circle does provide enough room to plant large tree species which have the potential to provide cooling shade if allowed to grow to maturity.

Unfortunately the use of mini-circles has raised concerns about their effectiveness. Some professionals have questioned whether they are large enough to have a real traffic calming effect, particularly for traffic traveling straight through the intersection. Others question whether American drivers are knowledgeable enough about the custom of yielding to traffic in the circle and signaling at the point of exiting. I personally also have concerns about the circle and the landscaping in it blocking a driver’s view of pedestrians crossing on the opposite side of the intersection (I nearly had a bad incident with a pedestrian as I was driving through a slightly larger roundabout in Germany. There it is common to place a tall mound of landscaped earth in the circle center, which in turn blocked my view of the pedestrian on the opposite side of the intersection. The near miss left me shaken.).

When I was taking pictures of the mini-circles I happened to strike-up a conversation with a man who is a local resident. He told me that he thought that the mini-circles were a bad idea since drivers don’t seem to know how to behave driving though them. According to his observations, it seemed that the drivers essentially ignore the yield signs and simply barge straight into the circle regardless of any other traffic that may be present and often doing so at speed. He said that he felt that the intersection was much safer when it was controlled by stop signs on all four corners. This gentleman’s personal observation seemed to reflect the concerns brought up by others regarding mini-circles.

Maybe some further refinements are required to make mini-circles more effective. Augment the mini-circles with the cobbled traffic islands leading up to and behind the intersections to help guide and slow motorists. If that is not enough maybe the inclusion of a speedhump on the approach to the intersection might bring vehicle speeds into compliance with what is intended for the mini-circle.

Beyond this one neighborhood, Princeton Borough and much of the immediate surrounding township is a walking and a relative cycling paradise. These didn’t just happen overnight. Like the all great walking and biking cities in Europe, Princeton has been working for many decades to provide accommodations for pedestrians and cyclists. Other facilities and innovations exist throughout the community and continue to be installed with just about every roadway improvement project. While the local governments may not have formal “Complete Streets” policies (they could now, I don’t know), it is clear that the spirit of such policy has long been in place. This and a long-standing policy of enforcing a pedestrian’s right-of-way in a crosswalk (well before it was sexy), makes Princeton one of New Jersey’s the leading bicycle and pedestrian friendly communities.

This pedestrian refuge island, located at the intersection of Mercer and Nassau Streets,
is being constructed as part of a routine roadway rehabilitation project.
The prior crossing was very long and would leave pedestrians exposed to traffic
for a great deal of time as they crossed, even more so for elderly pedestrians.
The large paved area also allowed drivers to make turns at high speed.
The refuge island provides pedestrians literal refuge from traffic,
a place to rest which is critical for those who require more time to cross and
a prevents drivers from taking the turn at high speeds since they must now negotiate
driving around the island.