Module 7 : Traffic Signal Design

Lecture 36 : Special Requirement in Traffic Signal

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	Effect of Lane Distribution Congestion and Delay at intersection particularly formed by to too many vehicles are moving same lane. So reduce that problem, we need to provide lane distribution. The lane distribution at intersection normally followed two categories. First one is the total volume of given approach are distributed by providing separate lane for left, right and through movement. For that individual movement, we need to fix some percentage of total flow at that particular approach. This type clearly defined in Figure 5 and following example. In second type, the given approach total volumes are separated by individual lane for left, right and straight. And straight moving vehicles also distributed into left and right turn lanes for unavoidable condition. If through movement vehicles are high, we need to follow second type distribution. Second type is explained in Figure 6 and example. Normally high straight cases we followed second method. In that second type divided into two distribution methods. First one is, through movement distributed into left, right and straight lanes. Second is, extra separate lane provide for through movement. So each cases some lane distribution factors are followed. That importance points are shown in following examples. Numerical example Find Critical Volume (Vi) for a Given 4 arm Intersection. Traffic flow Proportion of Left and Right turn are 10% and 20% respectively (For all approach). Left and Right turn Lane utilization factors are 0.2 and 0.3 respectively. Use following Phase Plan: Solution: From West to East, Left turn Traffic movement from total directional movement = 10% Right turn Traffic from total directional movement = 20% Through Traffic from total directional movement = 70% Left turning Vehicles = $2300\times 0.1 = 230~veh/hr$ Right turning Vehicles = $2300\times 0.2 = 460~veh/hr$ Through Movement Vehicles = $2300 \times 0.7 = 1610~veh/hr$ Lane Distribution Left turn utilization factor = 0.2 Right turn utilization factor = 0.3 Through traffic in Left turn Lane = $(2300\times 0.7)\times 0.2 = 322~veh/hr$ Through traffic in Right turn Lane = $(2300 \times 0.7)\times 0.3 = 483~veh/hr$ Through traffic in Median Lane = $(2300\times 0.7) \times 0.5 = 805~veh/hr$ From East to west, Left turn Traffic movement from total directional movement = 10% Right turn Traffic from total directional movement = 20% Through Traffic from total directional movement = 70% Left turning Vehicles = $1985\times 0.1 = 198~veh/hr$ Right turning Vehicles = $1985\times 0.2 = 397~veh/hr$ Through Movement Vehicles = $1985 \times 0.7 = 1390~veh/hr$ Lane Distribution Left turn utilization factor = 0.2 Right turn utilization factor = 0.3 Through traffic in Left turn Lane = $(1985\times 0.7) \times 0.2 = 278~veh/hr$ Through traffic in Right turn Lane = $(1985\times 0.7) \times 0.3= 417~veh/hr$ Through traffic in Median Lane = $(1985\times 0.7)\times 0.5 = 695~veh/hr$ From North to south, Left turn Traffic movement from total directional movement = 10% Right turn Traffic from total directional movement = 20% Through Traffic from total directional movement = 70% Left turning Vehicles = $1453\times 0.1 = 145~veh/hr$ Right turning Vehicles = $1453\times 0.2 = 291~veh/hr$ Through Movement Vehicles = $1453\times 0.7 = 1017~veh/hr$ From south to North, Left turn Traffic movement from total directional movement = 10% Right turn Traffic from total directional movement = 20% Through Traffic from total directional movement = 70% Left turning Vehicles = $1245\times0.1 = 124~veh/hr$ Right turning Vehicles = $1245\times 0.2 = 250~veh/hr$ Through Movement Vehicles = $1245\times 0.7 = 871~veh/hr$ $V_i = V_1+ V_2+ V_3+ V_4 = 804+695+871+1071 = 3442~veh/hr$