Heterogeneous Lanes’ Saturation Flow Rates at Signalized Intersections

Correct saturation flow rates are very important for the calculation of delays and level of service at intersections. However, the Highway Capacity Manual (HCM) procedure and the related studies assumed ideal conditions and cannot be applicable under mixed traffic circumstances. A traffic survey on 36 signalized intersections inside the Beijing's 5th Ring was conducted and a large number of experimental data with different lane types were statistically analyzed in this paper. Results show that the saturation headways approximately follow the normal distributions and the following base saturation flow rates are appropriate for Beijing intersections: 1380 passenger cars per hour per lane (pc/h/ln) of the right-turn lane, 1520 pc/h/ln of the left-turn lane, 1535 pc/h/ln of the through lane, 1457 pc/h/ln of the through-right lane and 1411 pc/h/ln of the through-left lane. These results have been used and verified in the real-time traffic information systems of Beijing Traffic Management Bureau.