Areas that are vulnerable such as pipebridges, overhead gantries etc should be clearly identified and height restrictions clearly marked.
The standard minimum clearance over every part of the carriageway of a public road is 16 feet 6 inches (5.03 metres). When the clearance over any part is less than this, standard warning signs both on and prior to the structure should be provided. The stated clearance should be at least 75mm less than the measured height.
Heights of vehicle likely to be encountered are 4.2 metres high (i.e. A standard container on a suitable flatbed vehicle). Minimum headroom provided should be 4.65 metres exclusive of any additional space required for lighting units. Where emergency vehicle access is required, the height of such vehicles should be confirmed with the relevant emergency service. Additional clearance will be required if there is a requirement for an overlay in the future. Changes in gradient may also reduce the effective headroom for long vehicles.