TRANSPORT PLANNING AND TRAFFIC ENGINEERING 4TH EDITION. CHAPTER 24: REGULATORY METHODS FOR TRAFFIC MANAGEMENT

Regulatory traffic management is based on law, and uses mandatory and prohibitory signs and markings to inform drivers what they must do and must not do in relation to speed, movement, and waiting. Speed limits are especially important in reducing the number and severity of road accidents; they also lead to smoother traffic flow and reduce fuel consumption. The worldwide trend is towards using absolute speed limits, above which it is always illegal to drive, rather than prima facie speed limits, above which some discretion is given to drivers. Congestion and accidents caused by turning vehicles at signal-controlled intersections may be handled by inserting an extra phase or adjusting the timing in the signal cycle, or by rerouting the turning traffic. One-way traffic operation is a simple regulatory tool for traffic relief, which does not need expensive policing; it has several advantages and disadvantages. In tidal flow operation, the total carriageway width is shared between two directions of travel, approximately proportional to the flow in each direction. Priority for high-occupancy vehicles is usually given to buses, but can also be given to full cars. Roadside parking needs careful regulation, but may be allowed for buses at bus stops, commercial vehicle loading and unloading, and residents' car parking. For the covering abstract, see IRRD 892228.