In general, traffic calming is introduced to reduce accident numbers and their severity within residential areas, but they can also be introduced for environmental reasons such as reducing "rat running" problems. Calming is mostly used in 20 mph zones to help make the lower speed limit self-enforcing.
Request new traffic calming engineering
We receive many requests for work each year, and to help make the best use of our limited funds and reach our targets for the reduction in accident numbers we carry out detailed analyses of the accident records to tackle the most deserving cases first.
Types of traffic calming
There are regulations governing the layout of speed humps. They must be spaced at regular intervals throughout the length of any road to which they are applied and must be within a minimum distance of the entry points to a road. Warning signs can be provided to identify speed humps but these are not required when the humps are located within a 20 mph zone.
The shape of speed humps is strictly regulated. They must be between 50 mm and 100 mm high, at least 2.75 m long and extend over the full width of the road, except for a drainage channel at either end. They may have round or flat tops.
Rochdale Borough has adopted 75 mm high humps as standard. This is because they have been found to reduce traffic speeds to around 22 mph.
In effect these are speed tables located within a junction. They are often constructed the full width of the carriageway so that they can provide a useful crossing point for pedestrians.
These are smaller versions of the standard speed hump and are usually positioned in pairs. On wider roads, 3 cushions may be used rather than 2.
Speed cushions are wide enough to allow wide wheel base vehicles such as buses and fire appliances to pass unhindered. Smaller wheel base vehicles like cars have to have at least 1 set of wheels partially on the cushion. This helps to slow cars down without having an effect on other traffic.
Speed cushions are often the preferred traffic calming solution for emergency services and bus companies. However, it is also necessary to introduce waiting restrictions to avoid parked vehicles diverting passing traffic out of alignment with the cushions.
Chicanes and build outs
Chicanes and build outs narrow the road and can be used to create a priority movement for vehicles. They reduce traffic speed by reducing the road width or creating a deflection. Not all locations are suitable for these types of features as they can remove on street parking and conflict with driveways.
Consultation of residents
Before introducing any traffic calming scheme that includes road humps we consult residents and the emergency services for their views. We also publish a formal Notice in the press with a 28 day period being allowed for objections to be submitted. All formal objections are considered and schemes are revised where appropriate.
Dangerous road junctions
We monitor accident data provided by Greater Manchester Police to highlight where clusters of accidents occur and look to introduce improvements to reduce the accident numbers.
We investigate requests for the introduction of safety schemes, but our priority is dealing with areas where accidents are occurring now.
20 mph speed limits and zones
20 mph speed limits exclude the use of any physical self-enforcing features and rely solely on signing and carriageway markings to encourage reduced traffic speeds. 20 mph speed limits can only be introduced on roads where average speeds are 24 mph or less.
20 mph zones require the introduction of a series of physical traffic calming measures like speed humps and chicanes to address lengths of road where average speeds exceed 24 mph in order to effectively make the lower speed limit self-enforcing. Entry points to 20 mph zones are clearly marked using distinctive signing and carriageway markings.
Speed indicator devices
Speed indicator devices can either display vehicle speeds back to the driver or display the relevant speed limit.
Funding from townships has to be obtained before any such signs can be introduced.