Vertical deflection devices

Vertical deflection devices are a type of traffic calming that creates a change in the height of the roadway to slow vehicle speeds and depending on the devices they can also make it easier or more comfortable for pedestrians to cross a street or intersection. For areas where pedestrians are anticipated, vehicle speeds in the case of a collision should be no greater than 30km/h and vertical deflection devices can be used to achieve this Safe System speed.

There are a range of vertical deflection devices that may be used at intersections to encourage slower vehicle speeds and thereby reduce the severity of an injury should a crash occur between a vehicle and a pedestrian (or between two vehicles)[1]: These include:

• road humps
• speed cushions / road cushions
• raised table / raised safety platform on approaches
• raised intersection.

The first two devices reduce vehicle speeds but do not assist pedestrians to cross. The latter two devices can also provide benefits to pedestrians crossing at intersections.

Vertical deflection devices can be installed at uncontrolled/priority intersections, signalised intersections and roundabouts.

Benefits

Providing raised platforms on the approach to an intersection or raising an intersection along with providing pedestrian facilities can help with the following:

• Raise the visibility of crossing pedestrians to approaching drivers particularly where the presence of crossing pedestrians is unexpected.
• Slows vehicle speeds before or through the intersection to give pedestrians and drivers more time to see each other and reduces the severity of a crash if it were to occur.
• Assist pedestrians to cross the road more easily. This can be particularly helpful where there are a high proportion of older pedestrians or pedestrians with mobility issues, however it can be more difficult for pedestrians who are blind, deafblind or have low vision to detect where the intersection is if there is no detectable kerb drop or tactile indicators. 

Implications 

When choosing a vertical deflection device at an intersection:

• Consider whether to raise the approach platform or raise the entire intersection. Raised intersections are generally more expensive due to increased footprint and greater potential impact on services and drainage.
• Careful consideration is required when using raised platforms on high speed streets as they may not reduce vehicle speeds to Safe System levels for pedestrians.
• There may be a need to reduce the speed limit to ensure the vertical deflection device can be safely traversed.
• If on a bus route, consider potential safety issues and discomfort to bus passengers. Careful design of the device will be required to accommodate heavy vehicles (eg buses).
• When choosing the type of vertical deflection consider potential safety issues and discomfort for people cycling.
• Appropriate drainage design is required.

Careful location and design of the ramp gradients is required to ensure Safe System speeds are met if pedestrians will cross the platform/intersection. This is context specific and depends on the layout and form of the intersection. Further guidance is provided in the design elements section for each intersection type.

PNG: Uncontrolled and priority controlled intersections

PNG: Signalised intersections

PNG: Roundabouts

Guidance for vertical deflection devices on bus routes is provided in the Public Transport Design Guidance.

PTDG: general clearance requirements

Signs and marking requirements for vertical deflection devices such as raised platforms/intersections are provided in Chapter 13 of TCD Manual Part 4.

TCD Manual Part 4 (draft for consultation)