This paper focuses on the implementation of the maximum likelihood technique to measure critical gap using data collected in the field. A methodology to define gap events is proposed, so that the accepted gaps and the largest rejected gaps could be obtained. The measurement at multi-lane sites and the treatment of major-street right-turn movement are specifically discussed. The paper points out some unusual situations where the proposed method cannot be applied directly. The proposed methodology has been used in NCHRP 3-46 to measure critical gaps under conditions in the U.S.A. (A)
Abstract