Review of Environmental Factors - Camden Valley Way Upgrade and Liz Kernohan Drive Extension (Final) - Flipbook - Page 720
Attachment B – Criteria for Interpreting SIDRA results and detailed SIDRA outputs
Criteria for Interpreting Sidra Results
1-Level of Service (LoS)
LoS
Traffic Signals and Roundabouts
Give Way and Stop Signs
A
B
C
Good
Good, with acceptable delays and spare capacity
Satisfactory
Good
Acceptable delays and spare
Satisfactory, but requires accident
study
D
Operating near capacity
E
At capacity, excessive delay: roundabout requires
other control method
Unsatisfactory, requires other control mode or
additional capacity
Near capacity and requires accident
study
At capacity, requires other control
mode
Unsatisfactory, requires other
control mode
F
2-Average Vehicle Delay (AVD)
The AVD is a measure of operational performance of an intersection relating to its LoS. The average
delay should be taken as a guide only for an average intersection. Longer delays may be tolerated at
some intersections where delays are expected by motorists (e.g. those in inner city areas or major
arterial roads).
LoS
Average Delay / Vehicle Traffic
Signals
(secs)
Roundabouts
and Give Way and Stop Signs
A
B
Less than 15
15 to 28
C
28 to 42
Good operation
Good with acceptable delays
and spare capacity
Satisfactory
D
42 to 56
Operating near capacity
E
56 to 70
F
Exceeding 70
Good operation
Acceptable delays and spare
capacity
Satisfactory but accident
study required
Near capacity, accident
study required
At capacity, excessive delays: At capacity; requires other
roundabout requires other control mode
control mode
Unsatisfactory,
requires Unsatisfactory,
requires
additional capacity
other control mode
3-Degree of Saturation (D/S)
The D/S of an intersection is usually taken as the highest ratio of traffic volumes on an approach to an
intersection compared with the theoretical capacity, and is a measure of the utilisation of available
green time. For intersections controlled by traffic signals, both queues and delays increase rapidly as
DS approaches 1.0. An intersection operates satisfactorily when its D/S is kept below 0.75. When D/S
exceeds 0.9, queues are expected.
