Empirical Study of Travel Time Estimation and Reliability

Table 1

Distribution form of 15 min travel time under different traffic conditions.

Signalized arterial link	Congested		Slow		Free flow
	<10 km/h		10 km/h to 30 km/h		>30 km/h
	Number	Percentile	Number	Percentile	Number	Percentile
Normal distribution (1)	12	0.136	23	0.155	13	0.169
Log-normal distribution (2)	23	0.261	55	0.372	35	0.455
Gamma distribution (3)	15	0.170	22	0.149	17	0.221
Weibull distribution (4)	38	0.432	48	0.324	12	0.156
Urban Expressway	Congested		Slow		Free flow
	<20 km/h		20 km/h to 50 km/h		>50 km/h
	Number	Percentile	Number	Percentile	Number	Percentile
Normal distribution (1)	10	0.222	48	0.142	16	0.050
Log-normal distribution (2)	12	0.267	149	0.442	181	0.569
Gamma distribution (3)	6	0.133	98	0.291	115	0.362
Weibull distribution (4)	17	0.378	42	0.125	6	0.019