Model

Category of independent variables

Model equation

Coefficient significance

R²

Linear type

Visible distance ( $x_1$ )

$y=-0.001x_1-0.001x_2-0.139x_3+15.440$

X

0.637

Traffic volume

( $x_2$ )

O

Speed ( $x_3$ )

X

Constant

O

Visible distance ( $x_1$ )

$y=-0.003x_1-0.001x_2+4.420$

O

0.570

Traffic volume ( $x_2$ )

O

Constant

O

Visible distance ( $x_1$ )

$y=-0.001x_1-0.153x_3+15.956$

X

0.552

Speed ( $x_3$ )

X

Constant

O

Visible distance ( $x_1$ )

$y=-0.002x_1+3.760$

O

0.471

Constant

O

Exponential type

Visible distance ( $x_1$ )

$y={\text{e}}^{-0.001x_1-0.0003x_2-0.052x_3+5.688}$

X

0.681

Traffic volume ( $x_2$ )

O

Speed ( $x_3$ )

X

Constant

O

Visible distance ( $x_1$ )

$y={\text{e}}^{-0.001x_1-0.0004x_2+1.567}$

O

0.630

Traffic volume ( $x_2$ )

O

Constant

O

Visible distance ( $x_1$ )

$y={\text{e}}^{-0.001x_1-0.058x_3+5.910}$

X

0.594

Speed ( $x_3$ )

X

Constant

O

Visible distance ( $x_1$ )

$y={\text{e}}^{-0.001x_1+1.286}$

O

0.530

Constant

O

Natural

log type

Visible distance ( $x_1$ )

$y=\text{ln}\left(-0.022x_1-0.029x_2-5.272x_3+517.81\right)$

X

0.419

Traffic volume ( $x_2$ )

X

Speed ( $x_3$ )

X

Constant

X

Visible distance ( $x_1$ )

$y=\text{ln}\left(-0.072x_1-0.031x_2+99.566\right)$

O

0.353

Traffic volume ( $x_2$ )

X

Constant

O

Visible distance ( $x_1$ )

$y=\ln \left(-0.017x_1-5.771x_3+536.003\right)$

X

0.346

Speed ( $x_3$ )

X

Constant

X

Visible distance ( $x_1$ )

$y=\ln \left(-0.071x_1+76.136\right)$

O

0.266