For the geometric and traffic characteristics shown below determine a suitable signal phasing system and phase lengths for the intersection using the Webster method. Show a detailed layout of the phasing system and the intersection geometry used.
Assume the following saturation flows:
Through lanes: 1600 veh/h/ln
Through-right lanes: 1400 veh/h/ln
Left lanes: 1000 veh/h/ln
Left-through lanes: 1200 veh/h/ln
Left-through-right lanes: 1100 veh/h/ln
What will be an ideal response?
Step 1: Calculate equivalent hourly flows
Step 2: Assume an intersection configuration, assign lane groups, and determine
critical volumes.
In this case, each approach was assumed to have one dedicated left-turn
lane, one through lane, and one through-right lane.
Step 3: Assume a phasing scheme and determine Yi , sum of critical ratios
Assume four phases as follows:
Sum Yi = 0.770
Step 4: Calculate lost time per cycle, using Equation 8.8
Assume lost time per phase due to acceleration and deceleration at phase changes
is 3.5 seconds and that an all-red interval of 1.5 seconds is provided at each phase.
Total lost time, L = 20 sec.
Step 6: Allocate green times
Allocated times are for green and yellow indications; appropriate length of
yellow interval can be subtracted from the total to give green times.
Total effective green time, Gte = C – L =135 seconds
(G+Y)1 = (0.177/0.770)(135) + 3.5 = 34.5 seconds
(G+Y)2 = (0.257/0.770)(135) + 3.5 = 48.5 seconds
(G+Y)3 = (0.140/0.770)(135) + 3.5 = 28.0 seconds
(G+Y)4 = (0.196/0.770)(135) + 3.5 = 37.9 seconds
Step 7: Ensure that green time required for pedestrian movement is provided,
using Equation 8.12.
Gp1 = 3.2 + (56/3.5) + (0.27)(1200/3600)(155) = 33.2 seconds
Gp2 = 3.2 + (56/3.5) + (0.27)(1200/3600)(155) = 33.2 seconds
Gp3 = 3.2 + (68/3.5) + (0.27)(1200/3600)(155) = 36.6 seconds
Gp4 = 3.2 + (68/3.5) + (0.27)(1200/3600)(155) = 36.6 seconds
Since Gp3 > (G+Y)3, the allocated sum of green and yellow time for phase
3 should be 36.6 seconds. Times are typically rounded up to the next whole
seconds; therefore, sum of green and yellow times are: G1 = 35 s; G2 = 49 s; G3 =
37 s; G4 = 38 s, resulting in a total cycle length of C = (35 + 49 + 37 + 38) +
(4)(1.5) = 165 seconds.
You might also like to view...
The four commonly used classifications of soils arranged in order of decreasing particle size are
A) gravel, silt, clay, and sand. B) gravel, sand, silt, and clay. C) gravel, sand, clay, and silt. D) gravel, silt, sand, and clay. E) none of the above.
Convert the circuits in Fig. 2.112 from Y to ?.
 FIGURE 1.png)
Types of communications include ________
A) Nonverbal B) Written C) Verbal D) All of these
Technician A says that a muffler is usually located on the discharge side of a compressor. Technician B says that a muffler can sometimes be located on the intake side of a compressor. Who is correct?
a.Technician A only b.Technician B only c.Both A and B d.Neither A nor B