Figure 4C-1 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 four 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) |
| 1400 |
80 |
1400 |
80 or 115* |
1400 |
115 |
| 1300 |
80 |
1300 |
90 or 115* |
1300 |
115 |
| 1200 |
80 |
1200 |
100 or 115* |
1200 |
145 |
| 1100 |
80 |
1100 |
120 |
1100 |
165 |
| 1000 |
100 |
1000 |
150 |
1000 |
200 |
| 900 |
120 |
900 |
175 |
900 |
240 |
| 800 |
150 |
800 |
200 |
800 |
275 |
| 700 |
180 |
700 |
250 |
700 |
340 |
| 600 |
220 |
600 |
290 |
600 |
390 |
| 500 |
260 |
500 |
340 |
500 |
460 |
| 400 |
310 |
400 |
390 |
400 |
Not available |
| * Note: 115 vph applies as the lower threshold volume for a minor-street
approach with two or more lanes and 80 vph applies as the lower threshold
volume for a minor-street approach with one lane. |
Return to Chapter 4C
| 