Road Humps are traffic calming devices that help in controlling the speed of the vehicles. The geometry of road humps affects the degree of discomfort experienced by the road users along with the speed controlling effect.

Road humps are also called speed humps that are suitable for almost all types of road layouts. These speed humps are also placed across the roads in series of several humps to prevent the speeding before and after the hump.

Also Read: Classification of Roads

Features of Road or Speed Hump

The speed humps are parabolic and vertical in structure which can be employed even for low speed and low volume roads. The dimension of speed humps is generally 3 to 4 inches in height with a width of 12 to 14 feet. This is also provided with a ramp length of 3 to 6 feet. These dimensions are calculated based on the target speed.

Speed Humps Made of Asphalt
Fig.1. Speed Humps Made of Asphalt

Provision of speed humps in roads helps to reduce the speed of the vehicles to a range between 15 to 20mph. Various studies have proved that the speed humps reduce the volume of the traffic by a whopping 18% which almost results in a reduction of collisions to 13%.

Design Criteria of Speed Humps

A safe speed hump must be designed based on the following criteria:

  1. The slopes greater than 1:10 is not recommended
  2. Slopes must not be less steep than 1:25
  3. The tapers must have side slopes not greater than 1:6
  4. The vertical lip of the speed hump must not be more than 1/4inch high.

The speed humps must be designated by using warning signs so that the approaching drivers are notified about the approaching humps. The humps are normally painted with pavement markings or highlighters to enhance its visibility. The ends of the speed humps are tapered to provide a gap for proper drainage.

The location of speed humps is more preferred in low-speed areas with a suitable traffic environment. These are used in residential roads and not preferred for major bus routes, primary emergency response router nor major roads. The placement of humps is mainly conducted in the mid-block between the intersections. The speed humps can be shaped circular or parabolic or sinusoidal.

Types of Speed Humps based on Shape
Fig.2. Types of Speed Humps based on Shape

Classes of Road Humps

There are basically two classes of humps:

  1. Short Humps
  2. Long Humps

1. Short Humps

Short humps are humps that can be straddled by all categories of wheels of normal vehicles. The response of vehicles towards the short humps is a function of their respective suspension characteristics.

Normally, short humps crossed with high speed do not provide any discomfort. But at lower speeds, the ride is unpleasant. The rider moves at a slower speed due to the fear of damage to the vehicles.

Also Read: Road User Characteristics

These humps administer a sharp jolt with the vehicle suspension during high speeds. At low speeds, as the axle passes over the hump, the vehicle body is deflected upwards.

2. Long Humps

These are humps that can be straddled by certain special vehicles especially large vehicles. These humps provide less severe ramp effect. Long humps demand long crossing time. Long humps create the effect of deflection of the vehicle body instead of the rapid deflection of tires or suspension.