A Group-Based Signal Timing Optimization Model Considering Safety for Signalized Intersections with Mixed Traffic Flows

Table 1

Observed traffic volumes driver behavioural parameters as well as estimated stop/pass decision models at the study site.

(a) Motorized vehicles

Signal Group	K1	K2	K3	K4	K5	K6	K7	K8	K9	K10	K11	K12
Traffic demand in pcu/h	44	328	184	235	486	100	200	311	155	212	573	25
saturation flow in pcu/h	1800	2000	1600	1800×2	2000×3	1600	1800	2000	1600	1800	2000×3	1600
Clearing Speed in km/h	35	47	35	35	47	35	35	47	35	35	47	35
Stop/Pass Decision Model	Left-turning				Straight-through				Right-turning

(b) Bicycles

Signal Group	K13	K14	K15	K16	K17	K18	K19	K20
Traffic demand in pcu/h	264	230	315	120	400	450	505	136
saturation flow in pcu/h	2000	3000	2000	3000	2000	3000	2000	3000
Clearing Speed in km/h	15	15	15	15	15	15	15	15
Stop/Pass Decision Model	Left-turning				Straight-through

For the sake of safety, take the 15 percentile clearing speed to make sure that most of the vehicles could clear the intersection.
According to HCM2010, because service quality deteriorates at flow levels well below capacity, the concept of capacity has little utility in the design and analysis of bicycle paths and other facilities. Thus it is hard to obtain the saturation flow of the bicycles during a unique or unambiguous theoretical method. In this case, results from one previous study on the saturation flow rate of bicycles in China were adopted.