User perceptions of signalised intersection level of service using fuzzy logic

Delay has been selected as the only measure for determining signalised intersection level-of-service (LOS). Previous studies reported that road users consider multiple factors in their evaluation of LOS, including traffic-related and non-traffic factors. The findings from more than 1300 responses to a web-based stated-preference survey suggest that road users consider multiple factors for the evaluation of signalised intersections. A methodology based on fuzzy logic is presented in this article to determine the signalised intersection LOS that explicitly accounts for user perceptions. To reflect the fuzziness of user perceptions, rigid LOS thresholds were replaced with fuzzy numbers. Fuzzy inferences were applied to combine important factors at signalised intersections for deriving a composite LOS measure. A case study with different improvement scenarios was conducted to illustrate the proposed method. Overall, the fuzzy logic method simulates the human reasoning process and provides a feasible alternative to quantify the user perceptions of signalised intersection LOS.