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Full-size image of Figure 4C-3

Figure 4C-3 shows the points at which the need for a traffic control signal shall be considered if an engineering study finds that for one hour (any four consecutive 15-minute periods) of an average day, the vehicles per hour on the major street and the corresponding vehicles per hour (VPH) on the higher-volume minor-street approach fall above the curve for the existing combination of approach lanes (see Section 4C.04 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)
1800 100 1800 100 or 150* 1800 150
1700 100 1700 100 or 150* 1700 150
1600 100 1600 120 or 150* 1600 170
1500 100 1500 145 or 150* 1500 180
1400 120 1400 155 1400 220
1300 130 1300 190 1300 250
1200 150 1200 220 1200 285
1100 175 1100 250 1100 340
1000 200 1000 285 1000 370
900 245 900 325 900 425
800 285 800 360 800 475
700 325 700 420 700 540
600 360 600 460 600 590
500 420 500 Not available 500 Not available
* Note: 150 vph applies as the lower threshold volume for a minor-street approach with two or more lanes and 100 vph applies as the lower threshold volume for a minor-street approach with one lane.

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