COMHAIRLE CONTAE ÁTHA CLIATH THEAS
SOUTH DUBLIN COUNTY COUNCIL

MEETING OF LUCAN AREA COMMITTEE

Tuesday, December 20, 2016

QUESTION NO. 12

QUESTION: Councillor E. O'Brien

"To ask the Chief Executive to confirm the current specification required for speed bumps used in the Lucan area?"

REPLY:

The provision of ramps on irish roads has gone through numerous legislative and guideline reuirements and recommendations over the years.

At present, entry and exit gradients should not exceed 1 in 10 or 1 in 15 on a bus route. Height should not exceed 75mm and the length cannot be less than 900mm.

The road must first be assessed in terms of whether or not it is a bus route and if a large bus platform or speed cushions could be used.

If it is not a bus route, then you establish if it is a round top or a flat top ramp that you are installing. If it is flat top, this will have to be longer in order for the entry and exit gradients reach the height of the footpath in order to facilitate crossing, hence, these ramps tend to be long. With this type of ramp, you need to provide gullies on the high side of the ramp because the ramp impedes water flow in the channel.

Round top ramps tend to be in more frequent use because once they are located within 8m of a public lighting column, not interfering with driveways and finished 300mm off the kerb line, they are more appropriate for residential areas.

Finally SDCC have developed a new ramp design based on all the foregoing that is expected to work well in the context of the 30kph speed limit. This ramp has an entry / exit gradient of 1 in 10, a maximum height of 75mm and a length of 2.5m. Ramps of similar geometry have been in use in the Paddocks for a numver of years.