Measurement of International Roughness Index by Using 𝑍-Axis Accelerometers and GPS

Table 6

Approximate values of the IRIs obtained using the model.

Link number	Right-wheel square root value	Left-wheel square root value	Actual IRI	Approximate IRI	Relative error (%)	Standardized residual
21	3.0182	4.3766	3.9041	4.109	4.98	0.78773
22	3.7904	4.3842	4.9140	4.566	7.61	−0.76443
23	3.4982	4.0119	4.2430	4.292	1.14	0.350071
24	3.1138	3.9016	3.6570	4.086	10.49	1.416846
25	4.4060	5.4115	6.5001	6.137	5.92	−0.80682
26	5.0087	5.5317	6.4629	6.020	7.36	−1.03084
27	5.7322	4.2199	3.9496	4.315	8.46	1.238302
28	4.9631	4.3613	4.4039	3.904	12.82	−1.19086