Back Continue

HCMAG Home
Overview
Introduction
Getting Started
Problem 1
Problem 2
Problem 3
Problem 4
Problem 5
Problem 6
Problem Index
Datasets
Search

 

Sub-problem 1a - Page 3 of 9

ID# C201A03

Sub-problem 1a: Maxwell Drive PM Peak Hour - Existing Conditions

Arrival Type Changes
Now let’s consider a parametric analysis: what happens if the arrival type changes from 2 to 1, 3, or 5 for the eastbound approach? For example, if we introduce coordination that improves eastbound progression, the arrival type could become 3, 4, or 5. If we make the progression worse by focusing the westbound flows, assuming there’s a tradeoff, it could become 1. From Exhibit 2-9 we can see that if the progression gets better, the eastbound delays could drop as low as 2.2 seconds for the left and 0.6 seconds for the through. (Dataset 2 shows inputs for the arrival type 3 and Dataset 3 shows inputs for arrival type 5.) These values are a small fraction of the base case. The average queue lengths could drop to 0.5 and 0.8 vehicles respectively. This urges an examination of coordination options. (Refer to Dataset 4 to see the details for arrival type 1). From Exhibit 2-9 we can also see that if the coordination gets worse (arrival type 1), the eastbound left-turn delay could increase to 27.2 seconds. That’s 45% more than the base case of 18.8 seconds. For the through movement, a similar increase could take place, from 5.3 to 8.0 seconds, a 50% increase. The average queue lengths could grow from 4.2 to 5.2 vehicles for the through movement (24% increase) and 1.8 to 2.3 vehicles for the left-turn movement (28% increase). In fact, the latter situation could be a problem. The left-turn storage capacity is only 5 vehicles and the 95th-percentile queue length (not shown in the table) is 4.7 vehicles; so with arrival type 1, we’re nearly at that limit.

Exhibit 2-9. Maxwell Drive Effects of Variations in the Eastbound Arrival Type 
Data-set EB Arrival Type Heavy Vehicles Phase Skip Signal Timing Performance Measure EB WB SB OA
L T R Tot L T R Tot L T R Tot
1 2 Yes Yes Base Delay 18.2 5.3 - 7.7 - 16.7 16.7 17.3 - 20.8 18.5 13.7
Queue 1.8 4.2 - - - 9.9 - 2.4 - 2.7 - -
2 3 Yes Yes Base Delay 11.9 3.5 - 5.0 - 16.7 16.7 17.3 - 20.8 18.5 12.7
Queue 1.3 2.9 - - - 9.9 - 2.4 - 2.7 - -
3 5 Yes Yes Base Delay 2.2 0.6 - 0.9 - 16.7 16.7 17.3 - 20.8 18.5 11.2
Queue 0.5 0.8 - - - 9.9 - 2.4 - 2.7 - -
4 1 Yes Yes Base Delay 27.2 8.0 - 11.5 - 16.7 16.7 17.3 - 20.8 18.5 15.1
Queue 2.3 5.2 - - - 9.9 - 2.3 - 2.7 - -

Discussion:
If we were to do a parametric study of arrival types for the westbound approach we’d find similar trends. The analysis would be useful, because better coordination ought to be possible with the signal at Clifton Country Road. What we’d need is a common cycle length and appropriate splits and offsets. It would also be useful to see if flow could be improved if we closed the exit from the fast food restaurant just east of the stopbar or did something to the intervening unsignalized intersection (with Old Route 146) that produces mid-block traffic that disrupts progression. We’ll look at these issues when we do Problem 6, the arterial analysis.

Back ] Continue ] to Sub-problem 1a