Critical Density of Experimental Traffic Jam

In a previous experiment, we have demonstrated that a traffic jam emerges without any bottleneck at a certain high density. In the present work, we performed an indoor circuit experiment in Nagoya Dome and estimated the critical density. The circuit is large (314m in circumference) compared to the previous experiment. Positions of cars were observed in 0.16m resolution. We performed 19 sessions by changing the number of cars from 10 to 40. We found that jammed flow was realized in high density while free flow in low density. We also found the indication of metastability at an intermediate density. The critical density is estimated by analyzing the density-flow relation. The critical density locates between 0:08 and 0:09 m(-1). It is consistent with that observed in real expressways.