Table 2.

Comparison of estimation methods.

	Linear arc	Google Maps	ArcGIS
Overall (N=29,935)
Mean absolute error in minutes* (SD)	4.8 (7.3)	3.5 (5.4)	4.4 (5.7)
Median absolute percent error* (IQR)	30.2 (14.4 to 52.2)	21.4 (10.0 to 40.0)	32.7 (17.0 to 49.8)
Range error in minutes	0 to 396	0 to 157	0 to 188
Percentage of estimates within one minute of observed time	19.8	23.9	16.7
Percentage of estimates within five minutes of observed time	79.0	86.6	81.3
Percentage of estimates within ten minutes of observed time	89.9	94.5	93.4
Transports < 10 minutes (n=14,321)
Mean absolute error in minutes* (SD)	2.9 (5.0)	2.4 (3.6)	2.6 (3.4)
Median absolute percent error* (IQR)	34.7 (16.7 to 58.1)	27.7 (12.5 to 50.0)	36.9 (19.2 to 54.7)
Range error in minutes	0 to 83	0 to 66	0 to 75
Percentage of estimates within one minute of observed time	26.2	29.6	23.8
Percentage of estimates within five minutes of observed time	89.8	91.3	92.6
Percentage of estimates within ten minutes of observed time	96.9	97.4	98.1
Transports > 20 minutes (n=3,610)
Mean absolute error in minutes* (SD)	12.7 (11.7)	9.8 (10.5)	11.6 (10.9)
Median absolute percent error** (IQR)	34.1 (15.2 to 59.1)	23.1 (10.0 to 45.5)	31.3 (15.0 to 55.3)
Range error in minutes	0 to 114	0 to 114	0 to 116
Percentage of estimates within one minute of observed time	6.9	8.6	6.0
Percentage of estimates within five minutes of observed time	31.6	42.3	30.6
Percentage of estimates within ten minutes of observed time	52.5	66.1	58.0

SD, standard deviation; IQR, interquartile range

^*All pairwise differences between methods were statistically significant with p-value <0.01.

^**Pairwise differences between linear arc and Google Maps and between Google Maps and ArcGIS were statistically significant with p-value <0.01. The difference between linear arc and ArcGIS had a p-value of 0.025.