## 3 Data
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Variables**} & \multirow{2}{*}{**Categories**} & \multicolumn{5}{c}{**Count(Ratio/\%)**} \\ \cline{3-6}  & & **Passenger Car** & **Motorcycle** & **Pickup** & **Truck** \\ \hline Number & & 11,419 & 9703 & 2913 & 5489 \\ Driver gender & Male & 9858 (86.3) & 8995 (92.7) & 2734 (93.8) & 5478 (99.7) \\  & Female * & 1561 (13.7) & 708 (7.2) & 179 (6.1) & 11 (0.2) \\ Driver age & \textless{}30 & 3515 (30.8) & 2204 (22.7) & 783 (26.9) & 687 (12.5) \\  & 30–60 * & 6214 (54.4) & 4064 (41.8) & 1722 (59.1) & 4219 (76.8) \\  & \textgreater{}60 & 1690 (14.8) & 3435 (35.4) & 408 (14.0) & 583 (10.6) \\ Drunk driving & Yes & 1718 (15.0) & 2512 (25.8) & 264 (9.1) & 33 (0.6) \\  & No * & 9701 (85.0) & 7191 (74.2) & 2649 (90.9) & 5456 (99.4) \\ Weather & Non-clear & 1575 (13.7) & 1219 (12.5) & 445 (15.3) & 866 (15.7) \\  & Clear * & 9844 (86.2) & 8484 (87.4) & 2468 (84.7) & 4623 (84.2) \\ Road surface & Non-dry & 1293 (11.3) & 984 (10.1) & 315 (10.8) & 632 (11.5) \\  & Dry * & 10,126 (88.7) & 8719 (89.9) & 2598 (89.2) & 4857 (88.5) \\  & Non-fixed object * & 8984 (78.6) & 7766 (80.0) & 2252 (77.3) & 4058 (73.9) \\  & Fixed object & 838 (7.3) & 1087 (11.2) & 188 (6.4) & 937 (17.0) \\  & Collision with pedestrian & 1492 (13.0) & 766 (7.8) & 434 (14.8) & 445 (8.1) \\  & Others & 105 (0.9) & 84 (0.8) & 39 (1.3) & 49 (0.8) \\ Week & Monday–Tuesday & 3314 (29.0) & 2780 (28.7) & 844 (29.0) & 1525 (27.8) \\  & Wednesday * & 1591 (13.9) & 1419 (14.6) & 419 (14.3) & 767 (13.9) \\  & Thursday–Friday & 3330 (29.2) & 2810 (29.0) & 841 (28.9) & 1653 (30.1) \\  & Weekend & 3184 (27.9) & 2694 (27.7) & 809 (27.8) & 1544 (28.2) \\ Month & Early in month & 3788 (33.1) & 3145 (32.4) & 933 (32.0) & 1783 (32.4) \\  & Middle in month * & 3730 (32.7) & 3249 (33.5) & 965 (33.2) & 1809 (33.0) \\  & Late in month & 3901 (34.2) & 3309 (34.1) & 1015 (34.8) & 1897 (34.6) \\ Season & Spring * & 2872 (25.2) & 2632 (27.1) & 762 (26.1) & 1532 (27.9) \\  & Summer & 2805 (24.6) & 2539 (26.1) & 676 (23.2) & 1415 (25.7) \\  & Fall & 3094 (27.0) & 2614 (26.9) & 782 (26.8) & 1573 (28.6) \\  & Winter & 2648 (23.1) & 1918 (19.8) & 693 (23.8) & 969 (17.7) \\ Light & Daylight * & 7314 (64.0) & 6011 (61.9) & 1966 (67.5) & 2946 (53.6) \\  & Dark (with street lighting) & 2485 (21.7) & 1661 (17.1) & 465 (15.9) & 798 (14.5) \\  & Dark (without street lighting) & 1620 (14.2) & 2031 (20.9) & 482 (16.5) & 1745 (31.7) \\ Crash time & Day * & 6561 (57.5) & 5345 (55.1) & 1780 (61.1) & 2550 (46.5) \\  & Night & 4858 (42.5) & 4358 (44.9) & 1133 (38.9) & 2939 (53.5) \\ Traffic & Controlled & 7603 (66.5) & 6376 (65.7) & 1874 (64.3) & 3668 (66.8) \\ control & Uncontrolled * & 3816 (33.4) & 3327 (34.2) & 1039 (35.6) & 1821 (33.1) \\ \hline \hline \end{tabular} Note: * indicates that variable was reference variable in model.  
\end{table} 
Table 1: Descriptive statistics of model variables across vehicle types. From Table 1, it can be seen that the proportion of risk factors varies with the types of motor vehicles. In detail, the proportions of female drivers in passenger car, motorcycle, pickup, and truck crashes were 13.7%, 7.2%, 6.1%, and 0.2%, respectively, highlighting a trend of gradual decrease. Furthermore, motorcycle crashes had higher percentages of older adult drivers (35.4%) than crashes of any other vehicle type, 14.8% for passenger car, 14.0% for pickup, and 10.6% for truck. Drunk driving was found to have similar effect on percentage value in crashes of the four vehicle types--25.8% for motorcycle, 15.0% for passenger car, 9.1% for pickup, and 0.6% for truck. However, a completely different phenomenon is represented by collision with fixed object. The proportion of collisions with fixed object related to truck crashes was 17% and was the highest, followed by motorcycle (11.2%), passenger car (7.3%), and pickup crashes (6.4%). The proportion of dark (without street lighting) condition in different motor vehicle types remained largely consistent with collision with fixed object.