Figure 4C-2 may be used in place of the graph in Figure 4C-1 if the posted
or statutory speed limit or the 85th percentile speed on the major street
exceeds 70 km/h (40 mph) or if the intersection lies within the built-up
area of an isolated community having a population of less than 10,000.
Like the previous figure, this figure shows the points at which the need
for a traffic control signal shall be considered if an engineering study
finds that for each of any 4 hours of an average day, the vehicles per
hour (VPH) on the major street and the corresponding vehicles per hour
on the higher-volume minor-street approach fall above the curve for the
existing combination of approach lanes (see Section 4C.03 for further
details). The figure displays three curves—one for each existing
combination of three approach lanes: one lane and one lane, two or more
lanes and one lane, and two or more lanes and two or more lanes.
The table below shows the approximate VPH on the major street and corresponding
VPH on the minor street for each combination of approach lanes.
|
One lane and one lane |
Two or more lanes and one lane |
Two or more lanes and two or more lanes |
| VPH on the major
street (Total of both approaches) |
VPH on the minor street
(Higher volume approach) |
VPH on the major
street (Total of both approaches) |
VPH on the minor street
(Higher volume approach) |
VPH on the major
street (Total of both approaches) |
VPH on the minor street
(Higher volume approach) |
| 1000 |
60 |
1000 |
60 or 80* |
1000 |
80 |
| 900 |
60 |
900 |
65 or 80* |
900 |
80 |
| 800 |
60 |
800 |
80 |
80 |
105 |
| 700 |
70 |
700 |
100 |
700 |
140 |
| 600 |
90 |
600 |
130 |
600 |
175 |
| 500 |
125 |
500 |
165 |
500 |
225 |
| 400 |
160 |
400 |
215 |
400 |
290 |
| 300 |
205 |
300 |
265 |
300 |
Not available |
| * Note: 80 vph applies as the lower threshold volume for a minor-street
approach with two or more lanes and 60 vph applies as the lower threshold
volume for a minor-street approach with one lane. |
Return to Chapter
4C
|
