Multimodal Level of Service Analysis for Urban Streets (2008) / Chapter Skim
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Pages 62-71
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From page 62... ...
Exclusive left-turn lane can be of any length or C H A P T E R 5 Auto LOS Model
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Variable tau Rank Correlation Coefficient Space Mean Speed 1.00 Total Travel Time 0.617 Lane Width -0.694 Number of Stops per Mile 0.270 Sign Quality 0.442 Tree Presence 0.474 Sidewalk Width -0.423 Has Ex Left-Turn Lane 0.264 Pedestrian Presence -0.445 Number of Signals per Mile -0.270 Control Delay per Mile -0.721 Speed Limit 0.381 Median Presence 0.147 Stops per Signal -0.462 Lane Marking Quality 0.111 Median Width 0.117 Variation in Speed -0.287 Number of Through Lanes -0.222 Separation Between Sidewalk and Travelway 0.104 Exhibit 66. Correlation Between Space Mean Speed and Other Explanatory Variables.
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The end result is a model of the following form Mean Auto LOS = 2.673 + 0.479 (Speed)
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Best Candidate Auto LOS Models Preliminary modeling analysis has resulted in two fairly strong models, one which uses number of stops per mile and the other which uses average space mean speed as the primary explanatory variable. Both models perform well.
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From page 66... ...
P(Y=6| x=2) Parameter DF Estimate Standard Erro r Wald Chi-Square Pr > ChiSq Intercept 1 1 -2.9189 0.2270 165.4053 <.0001 Intercept 2 1 -1.8273 0.2075 77.5198 <.0001 Intercept 3 1 -0.8529 0.2009 18.0246 <.0001 Intercept 4 1 0.2832 0.2005 1.9951 0.1578 Intercept 5 1 2.0937 0.2091 100.3006 <.0001 stops_per_mile 1 0.2033 0.0184 122.3357 <.0001 Pres__Of_Ex__LT_Lane 1 -0.5218 0.1111 22.0627 <.0001 Tree_Presence 1 -0.3379 0.0612 30.4761 <.0001 Parameters for Cumulative Regression Model Applied to Auto LOS -- Stops per Mile Model– Model 4 Exhibit 71.
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Correlation Coefficients of Auto LOS Models. Clip 2 - Comparing LOS Distributions of Test Data and Models 4, 5 and 6 (N=59)
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From page 68... ...
68 TEST MODEL 4 MODEL 5 MODEL 6 Clip 15 - Comparing LOS Distributions of Test Data and Models 4, 5 and 6 (N=42) - HCM LOS=1 0.00% 5.00% 10.00% 15.00% 20.00% 25.00% 30.00% 35.00% 1 2 3 4 5 6 LOS Rating (A=6 F=1)
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The best fitting model is Model 4, which uses stops per mile, presence of an exclusive left-turn lane and the presence of trees to estimate the observed LOS ratings. 5.2 Recommended Auto LOS Model The recommended auto LOS model (Model 6 above)
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If the exclusive left-turn lanes do not provide sufficient storage for left-turning vehicles, then the number of stops per mile would be affected, which would, in turn, adversely affect the perceived level of service. The attribute, Percent Speed Limit, is the ratio of the actual average speed (distance traveled divided by the average travel time for the length of the arterial including all delays)
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From page 71... ...
The HCM matched the video labs 26% of the time, while the proposed auto LOS Model 1 (stops) matched the video labs 69% of the time.
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