Road Degradation and Unsignalized Intersection Capacity in Kinshasa: A Gap-Acceptance Model
Description
Road congestion in Kinshasa, estimated to cost 1–3 billion USD per year, concentrates at predominantly unsignalized intersections, whose ca- pacity is governed by a gap-acceptance process—a queueing problem. This paper proposes a model based on Harders’ formula, calibrated on the mea- sured traffic volumes of the JICA Urban Transport Master Plan (2019) and on the critical-gap values of the Highway Capacity Manual. Linking the crit- ical gap tc to capacity μ, we show that at a measured priority flow of 2,000 PCU/h (30 Juin Boulevard), pavement degradation—lengthening the critical gap from 4 to 8 s—reduces unsignalized-intersection capacity by about 89 %, and that removing 58 % of the priority flow would be required to offset this loss without road repair; this last result is robust to the priority-flow value. The study provides a mechanistic interpretation of the JICA’s empirical ca- pacity factors and a quantified trade-off between pavement rehabilitation and demand reduction