Figure 4C-4 may be used in place of the graph in Figure 4C-3 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 one hour (any four consecutive 15-minute periods) 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.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.

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