Curb Radius Reduction

One of the common pedestrian crash types involves a pedestrian who is struck by a right-turning vehicle at an intersection. A wide curb radius typically results in high-speed turning movements by motorists. Reconstructing the turning radius to a tighter turn will reduce turning speeds, shorten the crossing distance for pedestrians, and also improve sight distance between pedestrians and motorists.

Nearby land uses and types of road users should be considered when designing an intersection so that curb radii are sized appropriately. If a curb radius is made too small, large trucks or buses may ride over the curb, placing pedestrians in danger.

Where there is a parking and/or bicycle lane, curb radii can be even tighter, because the vehicles will have more room to negotiate the turn. Curb radii can, in fact, be tighter than any modern guide would allow: older cities in the Northeast and in Europe frequently have radii of 2 to 5 ft without suffering any detrimental effects.

More typically, in new construction, the appropriate turning radius is about 15 ft and about 25 ft for arterial streets with a substantial volume of turning buses and/or trucks. Tighter turning radii are particularly important where streets intersect at a skew. While the corner characterized by an acute angle may require a slightly larger radius to accommodate the turn moves, the corner with an obtuse angle should be kept very tight, to prevent high-speed turns.

Considerations

1. Consider effective radii by taking into account parking and bicycle lanes.
2. Make sure that public maintenance vehicles, school buses, and emergency vehicles are accommodated.
3. Large trucks and buses may ride over the curb at intersections with tight radii, creating a danger for pedestrians who are waiting to cross.

Traffic Calming

Traffic calming is a way to design streets, using physical measures, to encourage people to drive more slowly. It creates physical and visual cues that induce drivers to travel at slower speeds. Traffic calming is self-enforcing. The design of the roadway results in the desired effect, without relying on compliance with traffic control devices such as signals, signs, and without enforcement. While elements such as landscaping and lighting do not force a change in driver behavior, they can provide the visual cues that encourage people to drive more slowly.

Experience has shown that traffic calming, if done correctly, reduces traffic speeds, the number and severity of crashes, and noise level.

Curb Extensions

Curb extensions—also known as bulb-outs or neckdowns—extend the sidewalk or curb line out into the parking lane, which reduces the effective street width. Curb extensions significantly improve pedestrian crossings by reducing the pedestrian crossing distance, visually and physically narrowing the roadway, improving the ability of pedestrians and motorists to see each other, and reducing the time that pedestrians are in the street.

Curb extensions placed at an intersection essentially prevent motorists from parking in or too close to a crosswalk or from blocking a curb ramp or crosswalk. Motor vehicles parked too close to corners present a threat to pedestrian safety, since they block sightlines, obscure visibility of pedestrians and other vehicles, and make turning particularly difficult for emergency vehicles and trucks. Motorists are encouraged to travel more slowly at intersections or midblock locations with curb extensions, as the restricted street width sends a visual cue to motorists. Turning speeds at intersections can be reduced with curb extensions (curb radii should be as tight as is practicable). Curb extensions also provide additional space for curb ramps and for level sidewalks where existing space is limited.

Curb extensions are only appropriate where there is an on-street parking lane. Curb extensions must not extend into travel lanes, bicycle lanes, or shoulders (curb extensions should not extend more than (6 ft) from the curb). The turning needs of larger vehicles, such as school buses, need to be considered in curb extension design.

Considerations

1. Curb extensions should only be used where there is a parking lane, and where transit and bicyclists would be traveling outside the curb edge for the length of the street.
2. Midblock extensions provide an opportunity to enhance midblock crossings. Care should be taken to ensure that street furniture and landscaping do not block motorists’ views of pedestrians.
3. Emergency access is often improved through the use of curb extensions if intersections are kept clear of parked cars. Fire engines and other emergency vehicles can climb a curb where they would not be able to move a parked car. At midblock locations, curb extensions can keep fire hydrants clear of parked cars and make them more accessible.
4. Curb extensions can create additional space for curb ramps, landscaping, and street furniture that are sensitive to motorist and pedestrian sightlines; this is especially beneficial where sidewalks are otherwise too narrow.

Crossing Islands

Crossing islands—also known as center islands, refuge islands, pedestrian islands, or median slow points—are raised islands placed in the center of the street at intersections or midblock to help protect crossing pedestrians from motor vehicles. Center crossing islands allow pedestrians to deal with only one direction of traffic at a time, and they enable them to stop partway across the street and wait for an adequate gap in traffic before crossing the second half of the street. Where midblock or intersection crosswalks are installed at uncontrolled locations, crossing islands should be considered as a supplement to the crosswalk. They are also appropriate at signalized crossings. If there is enough width, center crossing islands and curb extensions can be used together to create a highly improved pedestrian crossing. Detectable warnings are needed at cut-throughs to identify the pedestrian refuge area.

This kind of facility has been demonstrated to significantly decrease the percentage of pedestrian crashes. The factors contributing to pedestrian safety include reduced conflicts, reduced vehicle speeds approaching the island , greater attention called to the existence of a pedestrian crossing, opportunities for additional signs in the middle of the road, and reduced exposure time for pedestrians.

Curb extensions may be built in conjunction with center crossing islands where there is on-street parking. Care should be taken to maintain bicycle access. Bicycle lanes  must not be eliminated or squeezed in order to create the curb extensions or islands.

Speed Humps

Speed humps are paved (usually asphalt) and approximately 3 to 4 inches high at their center, and extend the full width of the street with height tapering near the drain gutter to allow unimpeded bicycle travel. Speed humps should not be confused with the speed “bump” that is often found in mall parking lots. There are several designs for speed humps. The traditional 12-ft hump has a design speed of 15 to 20 mph), a 14-ft hump a few miles per hour higher, and 22-ft table has a design speed of 25 to 30 mph. The longer humps are much gentler for larger vehicles.

Considerations

1. If the street is a bus route or primary emergency route, the design must be coordinated with operators. Usually, some devices are acceptable if used prudently — one device may be appropriate and may serve the primary need.
2. The aesthetics of speed humps and speed tables can be improved through the use of color and specialized paving materials.
3. Noise may increase, particularly if trucks use the route regularly.
4. May create drainage problems on some streets.
5. Speed humps and tables should be properly designed and constructed to reduce the chance of back problems or other physical discomfort experienced by vehicle occupants. Tight tolerances are required during construction.

Raised Intersections

A raised intersection is essentially a speed table for the entire intersection. Construction involves providing ramps on each vehicle approach, which elevates the entire intersection to the level of the sidewalk. They can be built with a variety of materials, including asphalt, concrete, stamped concrete, or pavers. The crosswalks on each approach are also elevated as part of the treatment to enable pedestrians to cross the road at the same level as the sidewalk, eliminating the need for curb ramps. Use detectable warnings to mark the boundary between the sidewalk and the street.

Considerations

1. Don’t use if on a sharp curve or if the street is on a steep grade.
2. May not be appropriate if the street is a bus route or emergency route. One device may be necessary and serve the primary need. Several raised devices may be disruptive, so other measures should be considered.
3. Speed tables and raised crosswalks and intersections can be an urban design element through the use of special paving materials.
4. Detectable warning strips at edges enable pedestrians with vision impairments to detect the crossing.
5. Care must be taken to manage drainage.

Raised Pedestrian Crossings

A raised pedestrian crossing is also essentially a speed table, with a flat portion the width of a crosswalk, usually 10 to 15 ft. Raised intersections and crosswalks encourage motorists to yield.

Considerations

1. Don’t use if on a sharp curve or if the street is on a steep grade.
2. May not be appropriate if the street is a bus route or emergency route. One device may be necessary and serve the primary need. Several raised devices may be disruptive, so other measures should be considered.
3. Speed tables and raised crosswalks and intersections can be an urban design element through the use of special paving materials.
4. Detectable warning strips at edges enable pedestrians with vision impairments to detect the crossing.
5. Care must be taken to manage drainage.

Landscaping

The careful use of landscaping along a street can provide separation between motorists and pedestrians, reduce the visual width of the roadway, and provide a more pleasant street environment for all. This can include a variety of trees, bushes, and/or flowerpots, which can be planted in the buffer area between the sidewalk or walkway and the street.

The most significant issue with any landscaping scheme is ongoing maintenance. Some communities have managed effectively by creating homeowners associations to pay for landscape maintenance or through the volunteer efforts of neighbors. Others have found them to be unreliable and budget for public maintenance instead. Consider adding irrigation systems in areas with extensive planting.

Choosing appropriate plants, providing adequate space for maturation, and preparing the ground can help ensure that they survive with minimal maintenance, and don’t buckle the sidewalks as they mature. The following guidelines should be considered: plants should be adapted to the local climate and fit the character of the surrounding area—they should survive without protection or intensive irrigation; and plant’s growth patterns should not obscure signs or pedestrians’ and motorists’ views of each other.

Considerations

• Maintenance must be considered and agreed to up-front, whether it is the municipality or the neighborhood residents who will take responsibility for maintenance.
• Shrubs should be low-growing and trees should be trimmed up to at least 8 to 10 ft to ensure that sight distances and head room are maintained and personal security is not compromised.
• Plants and trees should be chosen with care to match the character of the area, be easily maintained, and not create other problems, such as buckling sidewalks.