Delay is a complex measure and depends on a number of variables it is a measure
of driver discomfort, frustration, fuel consumption, increased travel time etc.
Total delay is the difference between the travel time actually experienced and
the reference travel time that would result during base conditions, in the
absence of incident, control, traffic, or geometric delay.
Also, Average control delay for any particular minor movement is a function of
the Capacity of the approach and The degree of saturation.
The control delay per vehicle for a movement in a separate lane is given by:
![$\displaystyle d_x = \frac{3600}{C_{mx}} +
900T\left[\left(\frac{V_x}{C_{mx}}-1...
...}{C_{mx}}-1)^2+\frac{\frac{3600}{C_{mx}}\frac{V_x}{C_{mx}}}{450T}}
\,\right]+5$](img1.png) |
(1) |
where,
 is the average control delay per vehicle for movement  in s/veh,
 is the capacity of movement or shared lane in veh/hr,
 is the analysis period h (15 min=0.25 h), and
 is the demand flow rate, movement or shared lane in veh/hr.
Four measures are used to describe the performance of TWSC intersections:
control delay, delay to major street through vehicles, queue length, and v/c
ratio.
The primary measure that is used to provide an estimate of LOS is control delay.
This measure can be estimated for any movement on the minor (i.e., the
stop-controlled) street.
By summing delay estimates for individual movements, a delay estimate for each
minor street movement and minor street approach can be achieved.
For AWSC intersections, the average control delay (in seconds per vehicle)
is used as the primary measure of performance.
Control delay is the increased time of travel for a vehicle approaching and
passing through an AWSC intersection, compared with a free flow vehicle if it
were not required to slow or stop at the intersection.
According to the performance measure of the TWSC intersection, LOS of the
minor-street left turn operates at level of service C approaches to
B.
Table 1:
Level of service criteria for TWSC intersection
| Level of Service |
Control delays(s/veh) |
| A |
0-10 |
| B |
 10-15 |
| C |
15-25 |
| D |
25-35 |
| E |
35-50 |
| F |
50 |
|
