70 miles per hour on a motorway and dual carriageway, and 60 miles per hour on a single carriageway road. In urban areas where there is electric street lighting the speed limit is 30 miles per hour unless otherwise signed. Low bridge signs Bridges with a clearance of less than are normally signed. Signs were formerly only in feet and inches, but from 2015 new or replacement signs must contain both imperial and metric measurements. The signs used at a low bridge depend on the type above the road. If a beam bridge with a horizontal clearance, the roundel is used and the limit is a prohibition. However if the bridge is an arch over the road, warning signs are used as the height varies across the width of the carriageway. Bridges particularly at risk from strikes may have a variable message sign that is activated by high vehicles passing through an infra-red beam. When the sign is activated four amber lamps flash, the top pair alternating with the bottom pair. Level crossing Signs Some level crossings in the United Kingdom do not have gates or barriers. These crossings will have several signs posted on approach and at the crossing. Bus and cycle signs Some roads and pavements are shared with cyclists and buses. The word "local" on the bus symbol means the only buses that may use the lane are those running a local service. Where the word "local" is not shown, the lane may be used by any vehicle designed to carry more than eight passengers, excluding the driver, and local buses. Solo motorcycles may use the lane where the motorcycle symbol is shown on the signs. Other vehicles may enter and stop in a bus lane to load and unload unless signs alongside the lane indicate otherwise. Pedestrian zone signs Areas such as high streets and shopping areas may be signed as "pedestrian zones". Restrictions are detailed on zone entry signs and repeater plates. The entry signs may indicate that buses, taxis, disabled badge holders or permit holders may enter the zone. Examples of zone entry signs include: Loading bays and Parking signs Both signs and road markings indicate waiting restrictions. On-street parking places may be designated for a particular class of vehicle (e.g. solo motorcycles or car) or a specific type of user (e.g. permit holders or disabled badge holders). Parking may be free or paid