Table 3 Simple and Multiple logistic regression models in predicting fatality based on Iranian-Integrated Road Traffic Injury Registry System (2015–2016)

Passenger include

 no

reference

reference

 yes

4.94 (4.53 to 5.40)

 < 0.001

4.95 (4.54 to 5.40)

 < 0.001

Pedestrian include

 no

reference

reference

 yes

2.56 (1.73 to 3.78)

 < 0.001

2.60 (1.75 to 3.85)

 < 0.001

Crash day

 weekday

reference

 weekend

1.05 (0.97 to 1.13)

0.235

Lightning status

 day

reference

reference

 night

1.64 (1.52 to 1.76)

 < 0.001

1.64 (1.52 to 1.76)

 < 0.001

 twilight/dawn

1.47 (1.25 to 1.73)

 < 0.001

1.48 (1.25 to 1.74)

 < 0.001

Weather

 clear/cloudy

reference

reference

 foggy/stormy/dusty

0.46 (0.2 to 1.06)

0.071

0.46 (0.20 to 1.05)

0.064

 rainy

1.30 (0.89 to 1.88)

0.172

1.32 (1.06 to 1.64)

0.014

 snowy

0.34 (0.14 to 0.84)

0.02

0.35 (0.15 to 0.83)

0.016

Zone type

 smooth

reference

 rough

1.18 (0.88 to 1.58)

0.259

 mountainous

1.08 (0.87 to 1.34)

0.465

Intersection control

 yes

reference

reference

 no

1.39 (1.29 to 1.51)

 < 0.001

1.40 (1.29 to 1.51)

 < 0.001

Line marking

 no line

reference

reference

 broken line

1.32 (1.18 to 1.49)

 < 0.001

1.36 (1.21 to 1.53)

 < 0.001

 single solid line

1.45 (1.22 to 1.71)

 < 0.001

1.54 (1.31 to 1.82)

 < 0.001

 double solid line

2.18 (1.29 to 3.68)

0.004

2.21 (1.31 to 3.75)

0.003

Road material

 sand/clay

reference

reference

 asphalt

1.89 (1.34 to 2.66)

 < 0.001

1.95 (1.39 to 2.73)

 < 0.001

Land use

 residential

reference

reference

 nonresidential

2.12 (1.90 to 2.37)

 < 0.001

2.15 (1.93 to 2.40)

 < 0.001

 other uni-purpose areas

1.58 (1.39 to 1.79)

 < 0.001

1.57 (1.38 to 1.78)

 < 0.001

 multi-purpose areas

1.24 (1.05 to 1.46)

0.012

1.25 (1.06 to 1.47)

0.007

Crash mechanism

 multiple-vehicle crash

reference

reference

 single-vehicle crash

1.13 (2.45 to 4.10)

0.051

1.20 (1.08 to 1.33)

 < 0.001

 involving vulnerable road users crash

1.70 (1.25 to 1.99)

 < 0.001

1.70 (1.50 to 1.92)

0.001

View obstacles

 no

reference

 yes

0.98 (0.79 to 1.23)

0.901

Crash position in the riding lane

 yes

reference

 no

1.08 (0.95 to 1.23)

0.224

Dry road surface

 yes

reference

 No

0.99 (0.73 to 1.37)

0.978

Curved geometric design

 No

reference

 yes

1.11 (0.99 to 1.25)

0.081

Vehicle factor

 no

reference

 yes

0.69 (0.47 to 1.03)

0.068

Human factor

 no

reference

reference

 yes

1.11 (1.02 to 1.21)

0.017

1.13 (1.03 to 1.23)

0.007

First cause

 irresponsibility

reference

reference

 need for more training

0.83 (0.75 to 0.91)

 < 0.001

0.83 (0.75 to 0.92)

 < 0.001

 need for more training & irresponsibility

1.46 (1.30 to 1.63)

 < 0.001

1.46 (1.30 to 1.64)

 < 0.001

 failure of organs

1.26 (0.59 to 2.68)

0.544

1.28 (0.61 to 2.68)

0.509

 multiple factors

2.82 (2.04 to 3.89)

 < 0.001

2.81 (2.04 to 3.87)

 < 0.001

Prior cause

 hasty driving & lack of attention to driving

reference

reference

 lack of attention to driving

0.93 (0.85 to 1.01)

0.096

0.93 (0.85 to 1.01)

0.095

 hasty driving

1.02 (0.89 to 1.17)

0.774

1.03 (0.89 to 1.18)

0.704

 lacked skill

1.17 (0.98 to 1.40)

0.089

1.16 (0.97 to 1.39)

0.097

 other

1.50 (1.29 to 1.75)

 < 0.001

1.48 (1.27 to 1.72)

 < 0.001

Direct cause

 regulation

reference

reference

 delay in sighting

1.34 (1.19 to 1.50)

 < 0.001

1.35 (1.20 to 1.51)

 < 0.001

 overspending

1.06 (0.91 to 1.22)

0.468

1.05 (0.91 to 1.21)

0.496

 Escaping crash in wrong way or multiple factor

1.07 (0.76 to 1.50)

0.704

1.06 (0.75 to 1.49)

0.738

Collision type

 side-swipe

reference

reference

 head-on

3.34 (2.85 to 3.91)

 < 0.001

3.35 (2.85 to 3.93)

 < 0.001

 rear-end

1.06 (0.91 to 1.24)

0.454

1.06 (0.91 to 1.25)

0.450

 T-bone

1.16 (0.99 to 1.36)

0.073

1.16 (0.99 to 1.36)

0.076

 fixed-object

2.30 (1.81 to 2.91)

 < 0.001

2.36 (1.87 to 2.99)

 < 0.001

Crash province

 Tehran

reference

reference

 Isfahan

1.48 (1.30 to 1.68)

 < 0.001

1.47 (1.30 to 1.67)

 < 0.001

 Fars

1.96 (1.70 to 2.26)

 < 0.001

1.95 (1.69 to 2.24)

 < 0.001

 Razavi Khorasan

1.13 (0.99 to 1.30)

0.075

1.12 (0.97 to 1.28)

0.112

 khuzestan

1.83 (1.60 to 2.09)

 < 0.001

1.83 (1.60 to 2.09)

 < 0.001

 East Azerbaijan

0.93 (0.77 to 1.13)

0.459

0.93 (0.77 to 1.12)

0.451

Commuting area

 urban

reference

reference

 suburban

3.21 (2.78 to 3.70)

 < 0.001

3.18 (2.76 to 3.67)

 < 0.001

 rural road

3.31 (2.69 to 4.08)

 < 0.001

3.26 (2.65 to 4.01)

 < 0.001

 exclusive urban area

1.75 (0.82 to 3.76)

0.149

1.71 (0.80 to 3.67)

0.169

 exclusive suburban area

3.08 (1.96 to 4.84)

 < 0.001

3.04 (1.94 to 4.78)

 < 0.001

Road type

 main street

reference

reference

 freeway

1.36 (1.09 to 1.68)

0.006

1.35 (1.09 to 1.68)

0.006

 expressway

1.83 (1.58 to 2.11)

 < 0.001

1.84 (1.59 to 2.13)

 < 0.001

 side street

1.22 (0.99 to 1.52)

0.066

1.22 (0.98 to 1.51)

0.076

 main road

1.82 (1.59 to 2.09)

 < 0.001

1.83 (1.59 to 2.10)

 < 0.001

 side road

1.39 (1.17 to 1.64)

 < 0.001

1.39 (1.17 to 1.65)

 < 0.001

 rural road

1.38 (1.12 to 1.69)

0.003

1.34 (1.09 to 1.65)

 < 0.001

 alley

1.17 (0.89 to 1.65)

0.062

1.18 (0.88 to 1.64)

0.067

Road shoulder

 paved with asphalt

reference

reference

 paved with soil

1.37 (1.22 to 1.52)

 < 0.001

1.38 (1.24 to 1.54)

 < 0.001

 unpaved

1.81 (1.61 to 2.05)

 < 0.001

1.84 (1.63 to 2.07)

 < 0.001

Road design

 one-way road

reference

reference

 separated two-way road

1.34 (1.20 to 1.49)

 < 0.001

1.34 (1.20 to 1.50)

 < 0.001

 unseparated two-way road

1.42 (1.27 to 1.58)

 < 0.001

1.40 (1.26 to 1.56)

 < 0.001

Road defect

 no

reference

reference

 signs defects

1.70 (1.42 to 2.04)

 < 0.001

1.72 (1.43 to 2.06)

 < 0.001

 geometric defects

1.23 (1.00 to 1.50)

0.045

1.26 (1.03 to 1.53)

0.023

 pavement/ lightning defects

1.42 (1.05 to 1.92)

0.024

1.43 (1.06 to 1.94)

0.020

 multiple defects

1.99 (1.66 to 2.39)

 < 0.001

2.00 (1.67 to 2.39)

 < 0.001

Road repairing

 no

reference

 yes

0.87 (0.63 to 1.19)

0.377

Vehicle type

 light

reference

reference

 heavy

1.42 (1.27 to 1.58)

 < 0.001

1.40 (1.26 to 1.56)

 < 0.001

 tricycle/ bicycle

0.43 (0.36 to 0.52)

 < 0.001

0.42 (0.35 to 0.50)

 < 0.001

Vehicle safety equipment

 yes

 no

0.91 (0.81 to 1.02)

0.097

Vehicle color

 low risk

reference

reference

 high risk

1.26 (1.17 to 1.36)

 < 0.001

1.26 (1.17 to 1.35)

 < 0.001

Vehicle life

 10 to 14 yrs

reference

reference

 less than 5yrs

0.89 (0.80 to 0.99)

0.025

0.90 (0.81 to 1.00)

0.054

 5 to 9 yrs

0.72 (0.65 to 0.78)

 < 0.001

0.72 (0.66 to 0.79)

 < 0.001

 15yrs and more

1.46 (1.28 to 1.68)

 < 0.001

1.46 (1.27 to 1.67)

 < 0.001

Vehicle plaque description

 personal regional

reference

reference

 other

2.73 (2.41 to 3.08)

 < 0.001

2.73 (2.42 to 3.09)

 < 0.001

Vehicle moving direction

 cardinal direct

reference

 ordinal direction

1.18 (0.85 to 1.63)

0.337

Vehicle maneuver

 turn

reference

reference

 forward

1.24 (1.00 to 1.53)

0.050

1.21 (0.98 to 1.49)

0.080

 overtake

2.17 (1.25 to 3.76)

0.006

2.22 (1.28 to 3.84)

0.004

 backward

1.95 (1.29 to 2.94)

0.002

1.89 (1.25 to 2.85)

0.003

 stop on the road

3.21 (2.18 to 4.72)

 < 0.001

3.08 (2.11 to 4.51)

 < 0.001

 other

3.90 (2.75 to 5.54)

 < 0.001

3.84 (2.72 to 5.44)

 < 0.001

Driver fault status

 not at fault

reference

 at fault

1.05 (0.96 to 1.15)

0.328

Driver gender

 female

reference

 male

1.02 (0.84 to 1.23)

0.868

Driver education

 academic

reference

reference

 illiterate

1.30 (0.97 to 1.73)

0.078

1.28 (0.96 to 1.71)

0.093

 primary

1.26 (1.00 to 1.58)

0.048

1.24 (0.99 to 1.56)

0.063

 nonacademic

1.60 (1.64 to 1.90)

 < 0.001

1.58 (1.33 to 1.88)

 < 0.001

Driver job

 jobs with high income

reference

reference

 jobs with middle income

1.49 (1.22 to 1.83)

 < 0.001

1.49 (1.22 to 1.81)

 < 0.001

 jobs with low income

2.48 (1.94 to 3.18)

 < 0.001

2.48 (1.95 to 3.15)

 < 0.001

Driver age

 adult

reference

reference

 child

1.07 (0.80 to 1.43)

0.658

1.08 (0.81 to 1.45)

0.598

 elderly

1.50 (1.27 to 1.77)

 < 0.001

1.50 (1.26 to 1.77)

 < 0.001

Driver license

 motorcycle

reference

reference

 class A

2.37 (1.52 to 3.71)

 < 0.001

2.40 (1.54 to 3.75)

 < 0.001

 class B

1.88 (1.22 to 2.91)

0.004

1.90 (1.23 to 2.94)

0.004

 class C

2.97 (2.25 to 4.62)

 < 0.001

3.03 (2.28 to 4.71)

 < 0.001

 no license

3.91 (2.50 to 6.12)

 < 0.001

3.93 (2.51 to 6.15)

 < 0.001

Driver seat belt

 used

reference

reference

 not used

1.55 (1.45 to 1.67)

 < 0.001

1.55 (1.44 to 1.67)

 < 0.001

Driver judiciary cause

 carelessness

reference

reference

 other

1.64 (1.41 to 1.91)

 < 0.001

1.67 (1.44 to 1.94)

 < 0.001

Driver misconduct

 spiral movement

reference

reference

 over speeding

1.31 (1.35 to 1.52)

 < 0.001

1.29 (1.33 to 1.50)

 < 0.001

 other

2.35 (2.47 to 2.84)

 < 0.001

2.51 (2.39 to 2.88)

 < 0.001