Continuous Freeway Illumination and Accidents on a Section of Rte. I-95

About the report:

Beginning with the oil embargo of 1973-74, highway lighting and particularly continuous lighting on freeways became one of the first items to be cut back to conserve energy and revenue. During this period of energy shortage, considerable lighting was turned off in Virginia and in particular the 13.8 km (8.57 mi) section of continuous lighting on I-95 between Springfield and Washington, D. C. By comparing the accident rate ratios for the lights turned off with those for the lights turned on it was found, in an earlier study, that the lighting decreased the night accident rate on this section of I-95 during the three-month period studied. Subsequently, the lights were reactivated. The study reported here extended the data to cover a six-month period and used a more refined approach in the analysis. For the period including December, January, and February, when heavy traffic volumes are on the I-95 roadway during the early hours of darkness, the lighting was found to be particularly effective in reducing the nighttime accident rate. For the March, April, and May period, when the hours of daylight lengthen, the night accident rate was improved; but the improvement was not found to be significant at the 95% confidence level, due, most likely, to the low number of accidents involved in the test. For the overall six-month period it was concluded that the lighting reduced the night accident rate. This finding was significant at the 95% confidence level. Evaluation of the night to-day accident rate ratios on an unlit control section of I-95 substantiated this finding. It was recommended that any plans for reducing energy consumption by turning off entire sections of freeway lighting should be carefully considered for possible adverse effects on the nighttime accident rate.

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