There are certain sections and unique points on the roads that require driving at moderate speed. Both when we drive on an urban road and when we drive on an interurban road we can encounter bumps or speed bumps on the road. These small obstacles are strategically placed on the road so that motorists slow down and pay special attention when driving.
The placement of these reinforcements on the pavement enhances road marking, which is, in general, the means used to achieve speed reduction in these sections. These devices not only serve as visual reminders for drivers, but also play a vital role in preventing accidents and protecting the safety of all road users.
The characteristics of these speed bumps are included in order FOM/3053/2008, of September 23, of the Ministry of Public Works (currently the Ministry of Transport, Mobility and Urban Agenda). The text details all aspects related to these elements, from the material with which they must be built and their geometry to the measurements they must comply with.
One of the speed bumps referred to in the ministerial order is legally known as a donkey's back. When talking about the most common speed bumps, the text specifically talks about two types: trapezoidal cross-section (raised pedestrian crossing) and donkey-backed. The latter are defined in the order of the Ministry of Public Works as “circular segment cross-section devices”.
The instruction states that the mission of speed bumps is to maintain a speed “that should have already been reduced with other measures (for example: signage, roundabouts, etc.), normally arranged at the beginning of the crossing or section.” Likewise, it specifies that when consecutive speed bumps are placed these bumps must be located between 50 and 200 meters, although it recommends that they be placed every 150 meters.
As a general rule, the donkey's back is usually placed on stretches of road where the speed is limited to 30 or 50 km/h. It is marked with three parallel triangles or arrowheads per lane that point in the direction in which the driver who will encounter it is traveling to facilitate visibility from afar.
Regarding measurements, the regulations establish that the donkey's back must measure 6 centimeters high and 4 meters long, although it contemplates a deviation of one centimeter high and 0.20 meters long. The order also states that this element must be made with non-deformable and durable materials, which is why it is usually made with rubber or durable plastics.
The donkey's back design is what differentiates this road device from the classic speed bumps that we can also encounter when driving. While traditional speed bumps usually have an entry and exit ramp leading to a flat surface, donkey backs take on a circular shape that resembles the back of a donkey, hence their characteristic name.
It is important to note that the donkey's back should not be confused with an elevated zebra crossing. Although the two speed bumps are intended to slow vehicles, the donkey's back stands out for its distinctive shape and its ability to force drivers to slow down more effectively.
