Module 5 : Uninterrupted Flow

Lecture 22 : Urban Streets

1

2

3

4

5

6

7

8

9

10

Step 6: Average travel speed

Arterial LOS is based on the 'average travel speed' for segment, section or entire arterial under consideration. Arterial average travel speed is given by

$$v_{avg}=\frac{3600L}{T_r\times L+D}$$ (1)

where, $v_{avg}$ = arterial or segmental average travel speed (Kmph), L = arterial or segmental length (Km), $T_r$ = total of the running time per kilometer on all segments in the arterial or section (seconds), D = total of the approach delay at all intersections within the defined arterial (seconds). It is the actual speed in consideration with the additional effect of control and all stop delays. It is the measure by which LOS is defined.

Step 7: Estimate the LOS

This is the last step of determination of LOS. After calculation of average travel speed we can determine the level of service of an arterial by using Table 1.

Table 1: Urban Street LOS by Class and Average Travel Speed

LOS	Average Travel Speed (km/h)
	I	II	III	IV
A	$>$ 72	$>$ 59	$>$ 50	$>$ 41
B	$>$ 56	$>$ 46	$>$ 39	$>$ 32
C	$>$ 40	$>$ 33	$>$ 28	$>$ 23
D	$>$ 32	$>$ 26	$>$ 22	$>$ 18
E	$>$ 26	$>$ 21	$>$ 17	$>$ 14
F	$>$ 26	$<$ 21	$<$ 17	$<$ 14

Numerical example

Consider an arterial which has free flow speed of 65 kmph and average running time of vehicles is 145 sec/km determine LOS for this arterial.

Solution: 

From Table 1 we can find LOS of an arterial. As free flow speed is 65 kmph by using table 3 we can classify this as Arterial Class II, Now we should know average travel speed, to find out LOS. Delay is determined in problem 1. Hence D=23.79sec/veh.

$$v_{avg}=\frac{3600L}{T_r\times L+D}=\frac{3600\times1}{145+23.79}=21.32~\mathrm{km/hr}$$

As average travel speed is 21.32 kmph we can have LOS as 'E' from Table 1.