Correspondence of Horizontal and Vertical Alignment with Safe Driving Conditions on Low-Volume Roads

Abstract

Since 1998, when the Gravel Roads Paving Program was started on the regional roads of the Republic of Lithuania, the length of gravel roads has shortened by 13.4% after reconstruction. It was discovered, however, that after reconstruction, 4.7% of gravel road sections became potentially dangerous. A disadvantage that was noted during implementation of the Gravel Roads Paving Program was a slightly changed or entirely unchanged horizontal alignment of the roads. In addition, after a gravel road is paved, the speed limit increases from 70 km/h to 90 km/h, as is allowed by traffic regulations, although the design speed of regional roads is 70 km/h and the road alignment was planned for that design speed. The horizontal alignment of 30 regional roads was investigated to assess the compatibility of horizontal alignment elements and their correspondence with traffic safety and to study the sight distance in vertical alignments. It was determined that compatibility of the horizontal alignment elements of regional roads was sufficient, but the estimated flow speed on these elements was 10 to 20 km/h higher than the design speed. Analysis of the sight distance, the stopping sight distance, and the passing sight distance in the vertical alignment of roads showed that in 90% of the cases, the sight distance was shorter than the stopping sight distance on a tangent.