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Problem

As roads are made wider, the crossing distances for pedestrians increase, creating a significant exposure of pedestrians to the high volumes of motor vehicles. With a typical pedestrian crossing speed of approximately 1 m (3.2 ft) per second, streets with four or more lanes in each direction can result in crossing times that require more than 30 seconds. In addition, lengthy crossings can make it impossible for pedestrians to see signal indicators on the far side of the crossing. Confusing multiple turning movements (often with protected signal phases) increase the potential for pedestrian crashes.

Background

In St. Petersburg, Florida, the intersection of Highway 98 at 74th Avenue North presented an extreme version of these conditions in the early 1990’s. Widened to nine lanes in each leg of the intersection, this intersection created a serious challenge for engineers to design a solution which could accommodate both pedestrians and motorists. The adjacent land included St. Petersburg Community College, a convenience store, an auto parts store, and a training center for the disabled. Some communities would have tried to build expensive solutions (such as overhead pedestrian bridges, for example) or simply ignored the problem, however, the designers of this project applied a combination of common sense, innovation, and creativity to create a solution that works within the available resources.

Solution

Michael Wallwork, the street’s designer, was asked by several community representatives to look at the intersection and explore alternatives to make it more pedestrian friendly. Accessibility was an important issue because a training center for wheelchair users was in the area. Since the designer was Australian, many of the design features came from Australia’s best practices.

The important issues included the following:

• Provide median noses that extend beyond the crosswalk to provide refuges for pedestrians.
• Narrow the lanes to minimize speeds, to shorten pedestrian crossing distances, and to widen the median.
• Add Australian standard right turn slip lanes, which are designed to keep pedestrians in the drivers’ line-of-sight, slow right turn vehicles to around 29 km/h (18 mi/h), and minimize the angle between turning vehicles and approaching vehicles to increase capacity and to reduce the angle drivers must to turn their heads.
• Add a bend in the middle of the crosswalk to meet the above requirements.
• Meet ADA standards with cut-throughs and ramps.

Results

For a retrofit of existing conditions, the pedestrian features of the Highway 98 intersection provide an excellent balance between pedestrian and motor vehicle needs. By reducing the pedestrian crossing time, providing right turn slip lanes, and reducing the all-red signal phase slightly, the ‘green’ time made available to motorists was actually increased and pedestrian safety was improved. With reduced lane widths, refuge islands at each corner and median refuges in the middle of each intersection leg, the maximum distance that a pedestrian has to cross is now only five lanes, or approximately 15 m (50 ft). This is a significant improvement over the prior conditions of crossing nine lanes of traffic in one signal phase. Overall crossing distances were reduced from over 55 m (180 ft) to approximately 40 m (130 ft).

Contact

Michael Wallwork
Alternate Street Design
1516 Plainfield Avenue
Orange Park, FL 32073
Phone: (904) 269-1851
Fax: (904) 278-4996
E-mail: mjwallwork@attbi.com

References

Background provided through e-mail interview with Michael Wallwork of Alternative Street Design. Original graphics provided by Dan Burden of Walkable Communities, Inc. and Jeff Olson, R.A.

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