Calming Traffic on Neighborhood Streets

In response to our post last month on targeted projects to support walking and cycling, a resident asked us to add traffic calming on Plummer Avenue to the list of recommended projects to enhance safety for pedestrians and cyclists. Like many of the streets that run from High Street down to Merrimack and Water Streets, Plummer Avenue experiences vehicle speeds that conflict with safe pedestrian movement. This is especially concerning because the sidewalks on many of our neighborhood streets are both too narrow for two people to walk abreast and in extremely poor condition, so walking in the street is more comfortable and feels safer.

From Storey Avenue through the South End, Newburyport has a street pattern that carries traffic efficiently across the city and distributes it to the neighborhoods. This simplified map shows the arterials that carry the through traffic – Merrimac St, High St and Low St – and the principal cross streets connecting them to each other and to the smaller neighborhood streets:

Many of these cross streets are much wider than they need to be. Newburyport’s minimum design standards for residential streets specify a minimum pavement width of 24 feet for “local” residential streets (streets that provide direct access to abutting properties with no through traffic) and 28 feet for “collector” streets (connecting local streets to arterials). However, these standards are primarily intended for streets in new residential subdivisions where vehicles can be parked off the street in private driveways and garages. Where the development pattern does not allow for off-street parking, widths of up to 36 feet may be appropriate, allowing for two 11-foot travel lanes and two 7-foot parking lanes. Often, though, the streets in the city’s older neighborhoods are narrower, sometimes having room for only one parking lane – or none at all.

The streets that run between High and Merrimac and between High and Low are classified as local streets, but in reality they also serve as minor collectors, bringing drivers from the arterials to the smaller neighborhood streets and also providing routes between the arterials. Several of these cross streets between High and Merrimac are significantly wider than the 36 feet needed for two-way traffic and on-street parking:

Street	Intersection	Pavement Width	Pavement > 36′
Oakland	Munroe	48′	12′
Tyng	Munroe	45′	9′
Broad	Munroe	43′	7′
Kent	Munroe	47′	11′
Green	Washington	44′	8′

These streets are as wide as, or even wider than, the arterial streets which they intersect. For example, Tyng Street is 45 feet wide at its intersection with Merrimac Street, yet Merrimac Street at that location measures only 33 feet curb to curb. At the other end, Tyng Street has about the same paved width as High Street even though it carries only a fraction of the daily traffic.

Many of these streets have intersections that are controlled by four-way stops, which help to keep speeds down. However, where stop signs don’t exist, the straight and overly wide streets encourage speeding. These elements of Newburyport’s street network that contribute to its efficiency in distributing traffic and providing access thus also create challenges for pedestrians of all ages.

On most local streets in Newburyport there’s no reason to drive faster than 20 mph. But simply reducing speed limits – and then attempting to enforce the reduced limits – has little if any effect on driver behavior. Drivers get their primary cues from the physical environment, and in many cases the design of our streets accommodates speeds that are faster than appropriate for residential neighborhoods. If we want to encourage walking and cycling, and if we want pedestrians of all ages to be able to walk safely, we need to reduce vehicle speeds on neighborhood streets, and the most effective way to do that is to make targeted physical changes to streets when warranted.

There are many proven techniques for reducing traffic speeds by adding physical elements to a street. The National Association of City Transportation Officials (NACTO) presents a comprehensive catalog of such speed reduction mechanisms in its Urban Street Design Guide. Some of these approaches could be appropriate for residential streets in Newburyport: for example, the images below show a speed hump (which can incorporate a raised crosswalk), a curb extension or “pinchpoint” (such as we have downtown on State St and now on High St near the High School), and a chicane.

An added benefit of horizontal measures such as curb extensions and chicanes is that they can provide space for amenities like landscaping. Here are two examples from Seattle showing how chicanes can be added to existing neighborhood streets to calm traffic as well as add greenery:

These chicanes were added to the streets without disrupting existing drainage patterns through the inclusion of runnels next to the curb. This is thus a very low-cost strategy with a direct impact on vehicle speeds.

Getting back to Plummer Avenue, while the pavement width isn’t excessive as for some other cross streets (it’s 29 feet at Christopher Street, almost the minimum for residential collector streets), the lack of intersection controls and the presence of the entrance to Atkinson Common may warrant a physical intervention to help slow down traffic. The most straightforward option would be to modify the crosswalk next to the park entrance. The existing crosswalk does not comply with current accessibility standards and should therefore be upgraded in any case. Two options, which could be implemented separately or together, are (1) to extend the curbs on both sides to visually narrow the street and (2) to make the crosswalk a raised crosswalk. Here are a few examples of raised crosswalks, with and without curb extensions::

Even where traffic calming isn’t an issue, some of the extra pavement could be reclaimed for stormwater management using natural systems. We’ll talk about that in another post.