Study Details
Study Title: Safety Effects of Reducing Freeway Illumination for Energy Conservation
Authors: Monsere and Fischer
Publication Date:JAN, 2008
Abstract: In 2001, Oregon's governor responded to a perceived future energy shortage in the Pacific Northwest by directing all state agencies to reduce power consumption by 10 percent. After review of power saving opportunities, the Oregon Department of Transportation (ODOT) elected to include selective illumination reductions on Oregon interstate highways as part of their energy saving strategy. The illumination reductions occurred at 47 interchanges and along 6.03 miles of interstate highway beginning between October 2001 and April 2002. The reductions consisted of full to partial interchange lighting, partial plus to partial interchange lighting, and lineal modifications. The study evaluated the changes in safety performance using crash, geometry, weather, and volume data from years 1996 to 2005 with an empirical-Bayes observational before-after evaluation. The study found a 3.47 percent increase (4.65 standard deviation) in total night crashes where full interchange lighting was reduced to partial lighting. Injury night crashes, however, were found to decrease by 11.38 percent. For interchanges where illumination was reduced from partial plus to partial, a 35.24 percent decrease in total night crashes was found. A 28.95 percent increase in total night crashes (18.21 standard deviation) on sections where the lineal lighting was modified was found. Weighing all evidence, the research concluded that a decrease in safety performance occurred on the lineal freeway sections and at full to partial lighting locations. An observed decrease in safety performance was not found at the partial plus to partial lighting modifications.
Study Citation: Monsere, C.M. and E.L. Fischer (2008). Safety Effects of Reducing Freeway Illumination for Energy Conservation. 87th Annual Meeting of the Transportation Research Board, TRB 2008 Annual Meeting CD-ROM.
CMFs Associated With This Study
Category: Highway lighting
Countermeasure: Full lineal to no or partial lineal lighting
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.905 | 9.5 |  | All | All | Principal Arterial Other Freeways and Expressways | Suburban |
| 0.766 | 22.4 | | All | A,B,C | Principal Arterial Other Freeways and Expressways | Suburban |
| 1.289 | -28.9 | | All | All | Principal Arterial Other Freeways and Expressways | Suburban |
| 1.392 | -39.2 | | All | A,B,C | Principal Arterial Other Freeways and Expressways | Suburban |
Countermeasure: Full to partial interchange lighting
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.984 | 1.6 | | All | All | Principal Arterial Other Freeways and Expressways | Suburban |
| 0.913 | 8.7 |  | All | A,B,C | Principal Arterial Other Freeways and Expressways | Suburban |
| 1.035 | -3.5 | | All | All | Principal Arterial Other Freeways and Expressways | Suburban |
| 0.886 | 11.4 | | All | A,B,C | Principal Arterial Other Freeways and Expressways | Suburban |
Countermeasure: Partial plus to partial interchange lighting
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 1.036 | -3.6 | | All | All | Principal Arterial Other Freeways and Expressways | Suburban |
| 0.862 | 13.8 | | All | A,B,C | Principal Arterial Other Freeways and Expressways | Suburban |
| 0.648 | 35.2 | | All | All | Principal Arterial Other Freeways and Expressways | Suburban |
| 0.6 | 40 | | All | A,B,C | Principal Arterial Other Freeways and Expressways | Suburban |
