Friday, June 23, 2017

Introducing the 2017 NJ Complete Streets Design Guide

The Traffic Calming Ad Hoc Task Group of Princeton's Complete Streets Committee would like to draw your attention to the newly issued 2017 NJ Complete Streets Design Guide (PDF, 25MB). Princeton's municipal decision makers now have an authoritative guide to traffic calming measures that has the seal of approval of the NJ Department of Transportation and the Federal Highway Administration. 

What has changed from prior advisories from the state – and makes this document truly significant – is that the NJ DOT now prioritizes safety and place making rather than speed and throughput for car traffic

"Traffic calming is a system of road design and management approaches that balances vehicular traffic on streets with other uses. It reinforces the idea that streets should create and preserve a sense of place instead of solely facilitating vehicles passing through at the greatest allowable speed."

We propose that the municipality use this guide, moving forward, in the implementation of our Complete Streets policy. In fact, the guide codifies the ongoing efforts of town staff and committees to calm traffic in Princeton to improve the safety and accessibility of all streets, in all neighborhoods, for all users of the roadway.

Need for Traffic Calming in Princeton


Traffic calming is an important component of road safety, as many studies have shown that in a crash, higher motor vehicle speeds cause more serious injury and more fatalities, particularly when the crash also involves a person on bike or on foot. This chart from the design guide shows that doubling speeds from 20 to 40 mph increases the risk of pedestrian fatalities by a factor of 17.

This map highlights the high number of car crashes in general on our busiest streets as well as specific danger spots.

NJDOT Car Crash data 2001-2014 by Code For Princeton 

Bubbles indicate number of car crashes; original interactive map here.


Princeton is home to a variety of streets including municipal and county roads, state and federal highways. Speeding occurs on all of them, as evidenced by data from speed cameras. In the graphs, the red line indicates the posted speed limit; the blue columns indicate the distribution of recorded speeds.

Speedcam data provided by the Princeton Police Department

When considering the data, please remember that studies have shown that "Your Speed Is" readouts are effective at reducing drivers' speed. One quantitative study shows that cars' speed is 3-8 mph lower when a "Your Speed Is" readout is present, compared to when it is not. The speedcam data therefore shows Princeton drivers at their best behavior, that is, more closely abiding by speed limits.

2017 NJ Complete Streets Design Guide 

The NJ Complete Streets Design Guide will enable Princeton to implement its Complete Streets policy with the assurance that strategies covered by the guide are evidence based and endorsed by NJDOT and FHWA.

The design guide provides:

  • guidance on adopting and implementing a Complete Streets policy, public policy changes that can help facilitate implementation, and strategies for integrating Complete Streets into the planning and design process; 
  • a range of tools and treatment options that can be used to enhance a street's safety, mobility, access, and vitality. This includes guidance on ADA accessibility.

The guide also corrects two widely held perceptions that are traditional barriers to making streets safe and accessible for all users. As the guide notes, contrary to these perceptions:

Posting a speed limit does not necessarily slow down cars. Among the guide's prescriptions to slow down car traffic are narrowing car travel lanes ("road diet" and "lane diet") and using visual cues that make drivers want to slow down. The guide describes many more effective strategies to slow traffic. 

Reduced vehicular capacity does not necessarily lead to congestion. The guide introduces the idea of traffic evaporation, which means that when road capacity is reduced, vehicle volumes can actually respond by decreasing in similar proportion. In other words, "If you don't build it, they won't come". 

Monday, June 19, 2017

Consultants' Findings from Princeton Parking Study

Consultants Nelson Nygaard presented findings from Princeton's ongoing Parking Study on June 14. A PDF file of the slides can be downloaded from Princeton's Parking Study page.

The presentation is packed with interesting information about the current parking situation in our town. Just to whet your appetite:

• There is a total of 7,025 parking spaces in the downtown core.
• Those parking spaces are at most 53% occupied (peak demand is at lunch time).
• The Spring Street municipal garage is used at a higher rate than the commercial garages due to lower pricing and validation options.
• Nearly 90% of customers and employees drive alone to downtown.

The presentation touches on a few ideas on parking management, but the main takeaway is this: Princeton needs to be pro-active about parking. We need to first determine what kind of parking availability we want, then design a parking system that will give us that kind of availability.

There is a suite of strategies to help us get there This could be an effective pricing structure. It could be a "payment in lieu" scheme where a new development is allowed to build less parking than specified by the town requirements, in lieu of an annual payment that could go towards funding - say - more public transit; It could be time sharing parking, e.g. where private parking restricted to office employees are opened to customers of restaurants after office hours. These are mentioned at the end of the presentation.

The updated numbers (total 7,025 parking spaces, of which 1,633 on-street) are significant for the Bicycle Master Plan. We have identified 176 on-street parking spaces on key corridors, removal of which would complete a low-stress bicycle network  (Witherspoon St and the Hamilton - Wiggins corridor). According to the updated numbers, those 176 spaces are 2.5% of the total number of parking spaces downtown.

Princeton's Engineering Department invites your comments and/or questions after reviewing the presentation. Please send them to The parking consultants will be formulating an approach over the summer; a public meeting to discuss draft strategies is slated for September.

Sunday, June 11, 2017

PBAC Research Relevant to Parking Study

With the opportunity of the Parking Study, the Princeton Bicycle Advisory Committee undertook research on parking policies for Princeton to encourage a Bike & Walk lifestyle that is healthier for residents and visitors, alleviates traffic congestion in our downtown core, helps Princeton decarbonize our transportation, and contributes to vibrant business districts.

Based on the findings, PBAC:

  • Requests inclusion of bicycle parking in the study;
  • Offers parking strategies that allows other communities to provide access for all.

Bicycle Parking

Even a cursory look at Princeton's streets show bicycles chained to parking meters, street furniture and trees. 

PBAC requests that bicycle parking be included in the parking study. Designated bicycle parking, such as on-street bike corrals, can free up sidewalk space for pedestrians. 

We refer to the chapter in the Bicycle Master Plan that covers parking, as well as to our earlier recommendations for bike parking (March, 2017).

We further suggest that large-scale bicycle parking be provided for special events with large attendance, such as Communiversity.

Accommodate bicycle lanes on corridors with high bicycle crash rates

In the PBAC recommendation (April 2017) on the Bicycle Master Plan we have proposed putting high priority on safe bicycle infrastructure on the corridors with high incidence of bicycle crashes: Witherspoon St, the Paul Robeson / Wiggins / Hamilton corridor (as well as North Harrison St). In the BMP, Parsons Brinckerhoff recommended that the car parking on these corridors be converted into bicycle lanes. 

Removing on-street parking on these key corridors would:

  • Encourage more bicycle traffic into the downtown area
  • Help restore the visual aspect of the historic core
  • Enhance the vibrancy of downtown businesses

Our research indicated that there are 176 car parking spaces along these corridors, or about 4% of the roughly 4200 spaces within the area of the current parking study.

On-Street Parking: priority for mobility-challenged

It is PBAC's position that destinations like the library, shops and restaurants must be accessible to everyone, regardless of their mobility.

We would therefore propose that priority for on-street parking be given to to the mobility challenged: the handicapped, the very elderly, and families with very young children. These designated parking spaces are to be sited on side streets as close as possible to the priority corridors (Witherspoon and Wiggins / Hamilton).

Time-share: parking / bike lanes

Princeton has an overnight parking ban on many of its streets, particularly in the downtown core. PBAC proposes that on corridors where this is appropriate, the overnight parking ban be replaced by a parking ban during daylight hours, when the parking lane is used as a bicycle lane.

On the other hand, in recognition that everyone has reasons for large celebrations several times during one's lifetime, we propose that designated bicycle lanes can be temporarily re-purposed as parking lanes, when properly marked as such, by permit from the town. This allows residents on streets with bike lanes to host large gatherings at their homes.

Intercept Parking outside historic center

Intercept parking keeps cars outside the downtown core, reducing traffic congestion and pollution. It is implemented in many cities and towns with an scenic or historic core. It helps reclaim the historic "feel" and contributes to both traffic calming and a vibrant retail sector. In Princeton's case, intercept parking spaces could be counted towards the number of spaces required for retail space.

Princeton University, as part of its campus expansion plan, is proposing to implement Intercept Parking: University staff and students commuting to Princeton from the Route 1 corridor are to be directed into a parking garage situated close to Route 1, from where they transfer onto either Tiger Transit or Zagster bikeshare to reach their destination on campus. 

In our municipality, a precedent for Intercept Parking has been set by the Harrison Street Shopping Center, which sponsored a free shuttle to and from Communiversity.

A bike share station as well as shuttle service is crucial for Intercept Parking sites that are farther removed than walking distance from Palmer Square. For shuttle service to be effective, its frequency should be four times per hour or more.

The map below indicates the existing downtown parking garages (red "P"s) and sites where Intercept Parking (blue "P"s) might be possible. These sites could be used to expand on the Intercept Parking site proposed by Princeton University.

Possible sites for intercept parking (blue "P" on map):

- Monument Drive lot [ Rt 206 intercept ] 

- YMCA lot [ Rt 206 intercept ] 

- Lot at Valley / Mt Lucas / Terhune [ Rt 206 intercept ] 

- Harrison St shopping center lot [ Rt 206 intercept ] 

- Whole Earth and/or Bank of America lots [ Rt 27 intercept ] 

- Princeton University site proposed near Washington Rd [ Rt 1 intercept ] 

Wayfinding signs are a crucial element of successful Intercept Parking design. If the parking sites are garages, an availability indicator can be built in with relative ease.

Where necessary, Intercept Parking can take the form of a multilevel parking garage, possibly suitable for mixed use (with e.g. retail at street level). Parking garages are extremely efficient in footprint, as is illustrated in the comparison between the Princeton core and Quaker Bridge Mall. 


Approx 2200 parking spaces within area shown of downtown Princeton (left map),

Approx 10,000 parking spaces at Quaker Bridge Mall (right map; both maps to same scale).

Managing Parking Demand through Pricing

PBAC acknowledges that the elimination of on-street parking in the corridors with high risk to bicycles will mean a decrease in parking revenue from those parking meters. 

We offer several proposals for redesigning the parking rate structure, both to recover revenue from removed on-street meters, and to incentivise biking and walking rather than taking the car into town:

  • On street parking to be shortest term and most expensive
  • Enforcement for on street parking to be tightened
  • Rates in the municipal garage (Spring St) to be the same as in commercial garages
  • Municipal garage to offer lower rates to those who need a car: the handicapped, the very elderly, families with very young children. The precedent for this is that the commercial garages offer reduced rates to church groups, nearby residents, etc.)
  • Rates can be raised for events like Communiversity and Commencement
  • Rates for Intercept Parking to be significantly lower than for downtown parking.

Currently, on-street parking on Nassau St is cheaper than in the municipal garage on Spring St, which in turn is cheaper than parking in the commercial garages. The chart assumes that you "feed" the on-street meter. It happens.