Table 3.

Fitting parameters of $P_{\mathrm{PE}}\left(v\right)=\widehat{q}{v}^{\gamma }$. Coefficients (with 95% confidence bounds).

Road	$\widehat{\mathit{q}}$	γ
Motorway	$16.89\times {10}^{-3}(15.78\times {10}^{-3},18.01\times {10}^{-3})$	$0.76(0.74,0.78)$
Trunk	$20.97\times {10}^{-3}(18.54\times {10}^{-3},23.62\times {10}^{-3})$	$0.79(0.75,0.83)$
Primary	$20.20\times {10}^{-3}(19.32\times {10}^{-3},21.10\times {10}^{-3})$	$0.77(0.76,0.79)$
Secondary	$24.82\times {10}^{-3}(23.64\times {10}^{-3},26.03\times {10}^{-3})$	$0.81(0.79,0.82)$
All	$49.52\times {10}^{-3}(48.63\times {10}^{-3},50.42\times {10}^{-3})$	$0.48(0.48,0.49)$