Speed bumps are very similar to humps. The main difference is that they tend to be more aggressively profiled, for increased effectiveness in slowing traffic. This means that speed bumps will have a steeper rise and tighter curvature to them than humps or ramps. They are often narrower front to back than a gentler, more gradual ramp.
Just like with humps, self-installed or temporary bumps are usually made from plastic or rubber. This is frequently manufactured using a modular design, for flexibility of width. They should also be fixed onto a solid concrete or asphalt surface using anchors or bolts. These are often included in the package and they are usually secured by passing the bolt through pre-drilled holes in the plastic body.
Speed bumps are recommended for use in areas where the standard driving speeds would already be no more than about 5-15mph. They aim to be effective in reducing actual speeds to around 2-5mph. As such, temporary bumps are a more aggressive form of traffic calming system than humps or ramps. Common examples of areas where speed bumps are used include car parks, private driveways, and entrance areas.
A speed table is a slightly different installation to either a bump or a ramp. Speed tables in the UK tend to be trapezium (trapezoid) shaped, meaning they have angled sides with a flattened top.
Speed tables are a longer and wider version of a speed ramp, which is why they are often called a flat top hump. They are usually installed to fill the entire width of a roadway. The flattened zone of a speed table is often deep and wide enough to allow the full wheelbase of a passing vehicle to sit on top. Where suitable markings and lights are added, they can often double as a raised pedestrian crossing.
A table is generally a less aggressive form of traffic calming. It is similar to a ramp, but with a milder impact on vehicle speed and ride quality. Speed tables are used for slightly reducing average speeds in places where more aggressive measures could cause a delay. For this reason, they are often located in busy areas with high traffic flow, such as at or near junctions.
Speed cushions are a series of smaller individual speed ramps or humps, placed side by side. They are usually positioned across the full width of a road, but with gaps left between them. Speed cushions can vary in severity from fairly mild to quite aggressive, depending on the location and necessary speed reduction.
The idea behind speed cushions is that, by spacing them apart width-ways, most vehicles will be forced to slow down. The spacing between speed cushions is planned such that consumer cars, trucks and SUVs can’t drive over them without one or both wheels coming into contact with a hump. Vehicles with a wider wheelbase - including many models of fire engines, ambulances and buses - should, in theory, be able to drive at higher speeds through the gaps. For greater flexibility in this regard, you will sometimes see an even smaller speed cushion positioned in the centre of a two-lane road, straddling the dividing line.
Speed cushions are much more common in the UK and Europe than in North America. This is because more domestic vehicles in the US and Canada have a wide enough wheelbase to drive through them unhindered.