Case study

The TfL London Digital Speed Limit Map (LDSLM) was first created in 2007 when Trevor Clark and his team undertook a survey of the entirety of Greater London, collecting all terminal and repeater speed limit signs. The result was a colour-coded GIS map (see image below) which was made available for satellite navigation units and was used by TfL in prototype Intelligent Speed Adaptation (ISA) vehicles.

Overview of the LDSLM, with Legend

The project was successful and TfL are currently rolling out the system on bus routes throughout London to improve road safety. As part of an ongoing contract with TfL, the BOM team regularly update and maintain the TfL LDSLM, mapping new speed limits that have come into force since the initial survey took place. The BOM team regularly checks the London Gazette for new speed limit Orders introduced by the London Boroughs and by TfL, before going out on-street with Tablet PCs in order to survey the area and ensure that the new Orders have been implemented. This method ensures the greatest level of accuracy.

TfL LDSLM speed limit changes are based on terminal sign locations

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