Identifying Lighting Conditions at Bikeway–Road Intersections for Cyclist Safety in Blacksburg, Virginia

Abstract

Lighting is an important factor in nighttime cycling, affecting both cyclists' ability to see the roadway environment and drivers' ability to detect cyclists. This thesis examines minimum vertical illuminance, defined as the lowest measured amount of light falling on a vertical plane at approximately cyclist eye height, at bikeway–road intersections in Blacksburg, Virginia. The study focuses on intersections between the proposed public bikeway network and Blacksburg-maintained public roads. I identified and validated 193 candidate intersections using GIS, then selected 36 sites through stratified random sampling by road class. Field measurements were conducted during two nighttime rounds at selected intersections: one under low moon illumination and one under high moon illumination. At each sampled intersection, I measured the minimum vertical illuminance at 1.5 m above the ground throughout each intersection and recorded the lowest measured value through ArcGIS Survey123. The findings show that minimum vertical illuminance was generally low across the sampled network. Although mean illuminance among the intersections increased from 1.4 lux in Round 1 to 1.8 lux in Round 2, the median remained very low, and the paired t-test showed no statistically significant difference between the two rounds. Threshold analysis showed that 28 intersections were at or below 1.5 lux in at least one measurement round. The main causes of underlighting were the absence of lighting infrastructure and insufficient lighting performance of existing lighting infrastructure. I developed a prioritization framework combining lighting deficiency, relative bicycle activity from the Strava heatmap, and road class. The process identified four Priority 1 locations for early review. The results suggest that field-based vertical illuminance measurement can help identify localized lighting deficits that may not be observable in broader roadway-level assessments. Overall, the study provides a planning-level framework for identifying, interpreting, and prioritizing underlit bikeway–road intersections for future lighting review.