Estimation of traffic flow parameters of U-turns

U-turns are widely used both on interurban highways and in urban streets. Estimation procedure regarding their traffic capacity was developed over 40 years ago. The calculated parameter values obtained were not specified for several decades. Therefore, we studied the operation of U-turns in order to specify calculation methods. The article considers such characteristics of the major and minor traffic flows as headways and lags. It presents research results as to the traffic volume influence on headways’ distribution and critical headway values in cases of U-turn facilities with the acceleration merging lane. We obtained a dependence connecting Erlang coefficient with traffic volume and a relationship characterizing the influence of traffic volume on critical headway values. We also established that minimal lags accepted by minor traffic flow drivers do not depend on traffic volume.