By Chris Sheffer, P.E.
Municipalities across the nation and world are facing the challenges of providing safe pedestrian crossings in an increasingly complex urban environment. Some of these challenges are manifested in providing pedestrian visibility and priority within a mid block crosswalk. Several cities, such as Salt Lake City, are experimenting with newer crossing approaches in an effort to accomplish this. These new approaches include: crosswalk markings, overhead beacons such as High Intensity Activated Crosswalks (HAWK), pedestrian signals with rest in walk and several more devices. In addition, at signalized or beacon locations pedestrian detection technologies such as photo electric bollards and pressure sensitive mats can provide varying degrees of effective passive detection at crosswalks. City Creek Center, a major recent redevelopment in the Salt Lake City downtown area, has also faced the challenge of these pedestrian issues.
DOWNTOWN TRAFFIC CONDITIONS
The downtown Salt Lake City area is a vibrant setting accessible by auto, bus, foot, bicycle and light rail (TRAX) with two stations currently located on Main Street and South Temple. Larger blocks make it more circuitous for pedestrians to cross at signalized intersections. The City has implemented various mid block crossing treatments appropriate to prevailing conditions at each location. These range from full pedestrian signals with rest in walk, overhead flashing yellow beacons, in pavement flashing lights, to pedestrian flags. Several locations with higher pedestrian activity already have signals that are phased for pedestrian rest in walk. During peak hours, motorized traffic activates the vehicular phases and the signal acts as a pre-timed signal. During the off peak times, pedestrians cross protected with the walk indication. This approach has been effective in the Temple area with few complaints. Pedestrian flags are orange flags that are available for pedestrians to carry across streets for added visibility to motorists. The implementation of this strategy has played a significant role in collision reductions of up to 20 percent.
City Creek Center Area
City Creek Center will include the redevelopment of two existing blocks of retail bounded by West Temple, South Temple, State Street and 100 South. This was the site of the ZCMI Center and Crossroads Plaza malls where three of the anchor stores will be redeveloped. The new mixed use development includes retail, apartments and office space and is a more dense development than the existing blocks.
CURRENT PRACTICES AND RESEARCH
The selection of an appropriate mid block crosswalk design has been subject to recent debate and reconsideration. Recent research efforts such as NCHRP 562 have found new safety relationships relative to crossing technologies and design approaches. The latest update to the Manual on Uniform Traffic Control Devices (MUTCD) will address changes in thinking regarding not only factors to consider in pedestrian crossing signal warrants, but also more guidance on other types of hybrid signals and beacons. In addition, the design walk speed used for pedestrian signal clearances of 4 feet per second will be revised to include a more conservative walk speed of 3.5 feet per second.
Recent research published in NCHRP 562 provides guidance to evaluating mid block treatments. In reviewing the strategy for addressing the type of treatment to implement at mid block crossings, the new MUTCD will also place a greater degree of emphasis on more of these factors. The following are some of the key factors that were found to be significant in considering treatment:
- Traffic Speeds – is the speed limit greater than 35 mph
- Pedestrian volumes - greater than 20 per hour to start the evaluation
- Major Street Volume – proposed to include a sliding scale based upon pedestrian volume and major street volume
- Number of lanes to cross – more than two lanes with no median refuge
- Distance to nearest signal – greater than 300 feet
- Downtown Core and proximity to transit stops
In addition, a graduated pedestrian and vehicular volume criteria is being proposed that would suggest a type of treatment.
Site Average and Range for Motorist Yielding by Crossing Treatment
Source:NCHRP 562
CROSSWALK TREATMENT DATA
The effectiveness and driver yield compliance of each crossing treatment is also important in the implementation decision. Most of the treatments shown above have been implemented in the downtown Salt Lake City area. These national data provide useful information on the statistics of driver’s yielding for each crossing treatments. If available, local data or experience is also important in verifying this for local conditions. These data suggest a significant increased benefit in the driver compliance for such treatments such as the HAWK over other flashing overhead beacons.
HAWK Example Source: NCHRP 56
LESSONS LEARNED
While the above approach can help decide the retro-fit of an existing crosswalk location through the use of existing data, projected pedestrian patterns from new development are not always easy to predict. While City Creek Center would provide an increase in development and motorized traffic (approximately 13.5k to 20k additional daily trips), the multimodal transportation options and mixed use development would result a higher mode share of non motorized modes. Pedestrian activity is expected to increase; however, the exact increase in pedestrian activity is not easily projected. Instead, this project provided pedestrian paths and crosswalks to encourage travel in specific locations. In the case of City Creek Center pedestrian activity was estimated on an order of magnitude basis from existing counts, future development use and general desire lines. This gave a starting point to evaluate appropriate options. In this case, proposed treatments were evaluated that would be appropriate for higher pedestrian activity, future expansion to a full signal, consistency with existing treatments, ease of maintenance, and in cases of new technology to the area, national effectiveness information.
The process for selecting a treatment was a collaboration between designers and City staff, and anticipated the new MUTCD signal criteria and national pedestrian safety data. While in pavement flashing lights have been more difficult to maintain and are no longer used, the City researched and concluded that the installation of HAWKs and flashing signs could be effective at selected locations. Pedestrian detection along with overhead flashing yellow beacons has been implemented at the mid block crossing at 200 South between Main Street and State Street. Photo electric bollards have been working adequately at this location, however; vendor opinions vary with accounts of bollards picking up false calls, and being easily knocked out of alignment. This design was evaluated as an option for two other locations. With the conceptual cost being higher for the bollards and the effectiveness of HAWKs being greater in stopping motorists, the HAWK option as shown below was selected.
As previously indicated, the selection of an appropriate crossing treatment could differ once the project activity stabilizes. The flexibility of a hybrid beacon to be converted to a full mid block signal was also attractive. Future pedestrian counts will be monitored to determine if and when a full mid block signal is warranted. This was also a factor in the decision to implement a hybrid beacon such as the HAWK.
Finally, with the unknown timing of the adoption of the new MUTCD, and knowing some of the guidance and recognition of newer hybrid beacons, flexibility in design was even more attractive. New MUTCD pedestrian volume warrants could make a full mid block signal more of a near term potential. The conversion of the HAWK to a full mid-block signal basically only requires a signal head and signing change.
Christopher R Sheffer, PE graduated from Michigan State University in 1982 with a BSCE. He also earned his Masters Degree from University of Colorado in 1996 and is currently an Associate for Fehr & Peers in Denver, Colorado. Mr Sheffer, a member of ITE, also sits on the Colorado Wyoming Section’s Executive Committee.
Fehr & Peers
621 17th Street
Denver, CO 80293
(303) 296-4300
ACKNOWLEDGEMENTS
Special thanks to Dan Bergenthal, PE of Salt Lake City for help and perspective on the City’s traffic and safety experiences in the downtown area.
REFERENCES
1. Traffic Operations Analysis for the City Creek Center, Fehr & Peers, 2007
Improving Pedestrian Safety at Unsignalized Crossings, NCHRP Report 562, National Cooporative Highway Research Program, Transportation Research Board, 2006