the suitability and effectiveness of humps for alerting drivers and controlling vehicle speeds have been investigated. seven vehicles including private cars, goods vehicles, a moped and a bus were used in the tests and six subjects made estimates of the noticeability and discomfort of the different humps at various crossing speeds. two main classes of hump have been studied, short humps which could be straddled by the wheels of most vehicles and long humps which could be straddled only by some large vehicles. the humps ranged from 2 in to 12 ft (0.05m to 3.66m) in length and from 0.5 in to 6 in (13mm to 152mm) in height. a hump 6 in (152mm) long with a height between 0.75 and 1.5 in (19 and 38mm) was capable of alerting drivers by producing a noticeable vibration. increasing the height of short humps introduced safety problems such as the risk of loss of control or of vehicle damage by grounding and increased the severity of impact on the tyres and vehicle suspension. increasing the length of a hump tended to reduce the hazard and a hump 12 ft (3.66m) long and 4 in (0.10m) high showed promise for controlling vehicle speeds. nevertheless the use of humps especially at sites where vehicle approach speeds are high should be undertaken with caution. (a).

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