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Thoroughfare planning objectives are achieved through both: (1) improving the <br /> operational efficiency of thoroughfares; and (2) improving the system efficiency <br /> through system coordination and layout. <br /> OPERATIONAL EFFICIENCY <br /> A street's operational efficiency is improved by increasing the capability of the <br /> street to carry vehicular traffic and people. In terms of vehicular traffic, a <br /> street's capacity is defined as the maximum number of vehicles which can pass a <br /> given point on a roadway during a given time period under prevailing roadway and <br /> traffic conditions. Capacity is affected by the physical features of the roadway, <br /> nature of traffic and weather. <br /> Physical ways to improve vehicular capacity include street widening, intersection <br /> improvements, improving vertical and horizontal alignment, and eliminating roadside <br /> obstacles. For example, widening of a street from two to four travel lanes more <br /> than doubles the capacity of the street by providing additional maneuverability <br /> for traffic. Impedances to traffic flow caused by slow moving or turning vehicles <br /> and adverse effects of horizontal and vertical alignments are thus reduced. <br /> Operational ways to improve street capacity include: <br /> (1) Control of access - A roadway with complete access control can often <br /> carry three times the traffic handled by a non-controlled access street <br /> with identical lane width and number. <br /> (2) Parking removal - Increase capacity by providing additional street width <br /> for traffic flow and reducing friction to flow caused by parking and <br /> unparking vehicles. <br /> (3) One-way operation - The capacity of a street can usually be increased <br /> 30-70%, depending upon turning movements and overall street width, by <br /> initiating one-way traffic operations. One-way streets can also improve <br /> traffic flow by decreasing potential traffic conflicts and simplifying <br /> traffic signal coordination. Pedestrian safety is enhanced since traffic <br /> moves in one direction rather than two. <br /> (4) Reversible lanes - Reversible traffic lanes may be used to increase <br /> street capacity in situations where heavy directional flows occur during <br /> peak periods. <br /> (5) Signal phasing and coordination - Uncoordinated signals and poor signal <br /> phasing restrict traffic flow by creating excessive stop-and-go <br /> operation. <br /> 2.2 <br />