The 1997 & 2000 HCM methodologies for analysis of all-way stop intersections are entirely new. The following is a summary its features:
Entirely new capacity formula and calculation procedures was provided, with an iterative capacity calculation step which can take more time to complete than the other LOS methods typically do.
The delay formula was modified.
New LOS thresholds were provided (see Table 15 1997 & 2000 HCM Unsignalized LOS Delay Thresholds).
Users should consult the 1997 & 2000 Highway Capacity Manual for details of these changes.
|
1997 & 2000 HCM Unsignalized LOS Delay Thresholds |
|
|
Level of Service |
Control Delay per Vehicle (secs) |
|
A |
< 10 |
|
B |
> 10 and < 15 |
|
C |
> 15 and < 25 |
|
D |
> 25 and < 35 |
|
E |
> 35 and < 50 |
|
F |
> 50 |
Table 15 1997 & 2000 HCM Unsignalized LOS Delay Thresholds
New data entry items for this methodology include the following:
Heavy vehicle percentage fields have been added
An option for calculating approximate capacity (this allows faster calculations by avoiding the iterative calculations, but accuracy is reduced)
A field has been added for entering the Alpha Value, which is a constant to adjust the degree of conflict probability to account for serial correlation between forecast headways (default=0.01)
A field for Analysis time Period has been added (default=0.25 hour)