Breakout Session 4: Identifying CRASH Problems 2015 Traffic Safety Conference by Srinivas Geedipally, Assistant Research Engineer, Texas A&M Transportation Institute

1. Systemic
Approach to
Safety in Texas
Srinivas Reddy Geedipally, PhD, PE
June 9, 2015

2. What is “Systemic Approach”?
 Focuses on high-risk roadway features
 Selects low-cost effective countermeasures
 Reduces fatal/severe crashes in rural areas
 Also beneficial for crash types less likely clustered
in urban area.
An approach that focuses on roadway safety
features to prevent high severe crashes

3.  Severe crashes are widely distributed
 Few locations experience a high number of
sustained occurrences
 Crash locations are somewhat random
 Addresses crashes across the network
Why “Systemic Approach”?

4. Systemic Project Selection Tool

5. Systemic Widening Program
 Rural
 2-Lane – 2-Way Highway
 ADT ≥ 400 vehicles per day
 Less than 24 foot paved surface width
 Widening to a maximum paved surface width of 28 foot
CRITERIA

6. Systemic Widening Program
 Head-On
 Single Vehicle Run Off Road
K & A Crashes

7. SVROR Crashes
Single Vehicle
8439
Urban
758 (11%)
Rural
6030 (89%)
Overturned
2485 (37%)
Fixed Object
4138 (61%)
Tree, Shrub, Landscaping - 1090 (26%)
Fence - 642 (16%)
Culvert-Headwall - 620 (15%)
Guardrail - 302 (7%)
Embankment- 260 (6%)
Ditch- 259 (6%)
Highway Sign - 224 (5%)
Other Fixed Object - 193 (4%)
Utility Pole - 150 (4%)
Mailbox - 148 (4%)
Others - 250 (6%)
Fatal and Incapacitating Injury Crashes Only
Two-lane Two-way Highways
Source: TxDOT CRIS, 2009-2013
Other/Unknown
165 (2%)
Minor Arterial - 342 (45%)
Collector - 215 (28%)
Principal Arterial - 196 (26%)
Others - 5 (1%)
Major Collector - 3327 (55%)
Minor arterials - 1386 (23%)
Minor Collector - 751 (12%)
Principal Arterial - 557 (9%)
Local - 9 (1%)
Total Paved Width
18-20: 1187 (20%)
21-22: 487 (8%)
23-24: 927 (15%)
25-26: 313 (5%)
27-28: 483 (8%)
29-30: 304 (5%)
31-40: 1142 (19%)
>40: 1187 (20%)
On Roadway
1651 (20%)
ROR
6788 (80%)
Fatal - 2167 (26%)
Incap. injury- 6272 (74%)
ADT
0-399: 768 (13%)
400-999: 1277 (21%)
1000-1999: 1432 (24%)
2000-2999: 887 (15%)
3000-3999: 554 (9%)
4000-4999: 356 (6%)
5000-5999: 250 (4%)
6000-6999: 182 (3%)
7000-7999: 99 (2%)
8000-8999: 79 (1%)
9000-9999: 46 (1%)
>=10000: 100 (2%)

8. Head-on Crashes
Head-on
2023
Fatal and Incapacitating Injury Crashes Only
Two-lane Two-way Highways
Source: TxDOT CRIS, 2009-2013
Minor Arterial - 160 (45%)
Principal Arterial - 120 (34%)
Collector - 69 (19%)
Others - 9 (2%)
Major Collector - 633 (38%)
Minor arterials - 584 (35%)
Principal Arterial - 376 (23%)
Minor Collector - 72 (4%)
ADT
0-399: 37 (2%)
400-999: 113 (7%)
1000-1999: 253 (15%)
2000-2999: 282 (17%)
3000-3999: 229 (14%)
4000-4999: 199 (12%)
5000-5999: 152 (9%)
6000-6999: 141 (8%)
7000-7999: 80 (5%)
8000-8999: 62 (4%)
9000-9999: 31 (2%)
>=10000: 86 (5%)
Urban
358 (18%)
Rural
1665 (82%)
Fatal - 1015 (50%)
Incap. injury- 1008 (50%)
Total Paved Width
18-20: 139 (8%)
21-22: 85 (5%)
23-24: 151 (9%)
25-26: 43 (3%)
27-28: 121 (7%)
29-30: 66 (4%)
31-40: 413 (25%)
>40: 647 (39%)

9. Evaluate Risk Factors
Average Daily Traffic
Highways are categorized into:
 Low volume: 400 < ADT <700
 Moderate volume: 700 < ADT <1500
 High volume: ADT > 1500

10. Evaluate Risk Factors
Cross-sectional width
- Crash Total
- Crash Over-Representation
a) SVROR crashes
b) Head-on crashes
60.7%
6.4%
32.8%
53.3%
6.6%
40.2%
0.0%
20.0%
40.0%
60.0%
80.0%
<=10+0 10+1 11+0
Percent
Lane Width + Shoulder Width (ft)
Length
KA Crashes
60.7%
6.4%
32.8%
63.1%
7.1%
29.8%
0.0%
20.0%
40.0%
60.0%
80.0%
<=10+0 10+1 11+0
Percent
Lane Width + Shoulder Width (ft)
Length
KA Crashes

11. Evaluate Risk Factors
Truck Volume
a) SVROR crashes
b) Head-on crashes
49.6%
32.9%
17.5%
56.2%
30.0%
13.8%
0.0%
15.0%
30.0%
45.0%
60.0%
75.0%
0-8% 9-15% >15%
Percent
Truck Presence
Length
KA Crashes
49.6%
32.9%
17.5%
59.8%
18.9% 21.3%
0.0%
15.0%
30.0%
45.0%
60.0%
75.0%
0-8% 9-15% >15%
Percent
Truck Presence
Length
KA Crashes

12. Evaluate Risk Factors
Alignment
a) SVROR crashes
b) Head-on crashes
3.7%
18.2%
78.1%
14.8%
22.1%
63.1%
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
Curve (R <1000ft) Curve (R >=1000ft) Straight
Percent
Alignment
Length
KA Crashes3.7%
18.2%
78.1%
10.6%
19.0%
70.4%
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
Curve (R <1000ft) Curve (R >=1000ft) Straight
Percent
Alignment
Length
KA Crashes

13. Evaluate Risk Factors
Risk Factor Weights
Category
Weight (points)
0 1 2 3 4 5 6 7 8 9 10
Crash Total
≥0%
and
<10%
≥10
and
<20%
≥20
and
<30%
≥30
and
<40%
≥40
and
<50%
≥50
and
<60%
≥60
and
<70%
≥70
and
<80%
≥80
and
<90%
≥90
and
<100%
100%
Crash Over-
Representation
0%
>0%
and
<2%
≥2%
and
<3%
≥3%
and
<4%
≥4%
and
<5%
≥5%
and
<6%
≥6%
and
<7%
≥7%
and
<8%
≥8%
and
<9%
≥9%
and
<10%
≥10%
and
≤100%

14. Evaluate Risk Factors
SVROR Risk Factor
Weight (points)
Low Volume
(400≤ADT≤700)
Moderate
Volume
(700<ADT≤1,500)
High Volume
(ADT>1,500)
Lane & Shoulder
Width
10+0 7 8 8
10+1 0 1 1
11+0 6 2 2
Truck Percentage
≤8% 2 7 11
9-15% 10 3 3
>15% 3 2 1
Alignment
Curve (R
<1000ft)
8 8 7
Curve (R
≥1000ft)
1 3 2
Straight 7 6 7

15. Evaluate Risk Factors
Head-on Risk Factor
Weight (points)
Low Volume
(400≤ADT≤700)
Moderate Volume
(700<ADT≤1,500)
High Volume
(ADT>1,500)
Lane & Shoulder
Width
10+0 7 6 5
10+1 4 2 1
11+0 2 6 11
Truck Percentage
≤8% 2 2 15
9-15% 4 6 1
>15% 6 2 5
Alignment
Curve (R
<1000ft)
12 11 11
Curve (R
≥1000ft)
1 2 5
Straight 6 6 6

16. Evaluate Risk Factors
We now have
 Weight for SVROR (Ws)
 Weight for Head-on (Wh)
Total Weight
𝑊𝑡 = 𝑊𝑠 + 𝑝 ∗ 𝐶 ∗ 𝑊ℎ
Where
• 𝑝= proportion of the number of head-on crashes with respect to
SVROR and
• 𝐶 = proportion of the crash cost of head-on crashes with respect
to SVROR.

17. Evaluate Risk Factors
Combined Risk Factor
Weight (points)
Low Volume
(400≤ADT≤700)
Moderate
Volume
(700<ADT≤1,500)
High Volume
(ADT>1,500)
Lane & Shoulder
Width
≤10+0 8.93 9.66 9.38
10+1 1.10 1.55 1.28
11+0 6.55 3.66 5.04
Truck Presence
≤8% 2.55 7.55 15.14
9-15% 11.10 4.66 3.28
>15% 4.66 2.55 2.38
Alignment
Curve (R
<1000ft)
11.31 11.04 10.04
Curve (R
≥1000ft)
1.28 3.55 3.38
Straight 8.66 7.66 8.66

18. Practical Application
DFO = 1.68
DFO = 1.73
DFO = 1.76
DFO = 1.8
𝐿 𝑐 = 0.03 mi
𝐿𝑡1 = 0.05 mi
𝐿𝑡2 = 0.04 mi
Highway: BS0121D
District: Paris
County: Fayette
DFO: 1.68 to 1.8
Total Length :0.12 miles
ADT (in 2013): 516 vpd
Truck %: 8.9
Lane Width: 10 ft
Shoulder Width: 0 ft
R = 110 ft

19. Evaluate Risk Factors
Combined Risk Factor
Weight (points)
Low Volume
(400≤ADT≤700)
Moderate
Volume
(700<ADT≤1,500)
High Volume
(ADT>1,500)
Lane & Shoulder
Width
≤10+0 8.93 9.66 9.38
10+1 1.10 1.55 1.28
11+0 6.55 3.66 5.04
Truck Presence
≤8% 2.55 7.55 15.14
9-15% 11.10 4.66 3.28
>15% 4.66 2.55 2.38
Alignment
Curve (R
<1000ft)
11.31 11.04 10.04
Curve (R
≥1000ft)
1.28 3.55 3.38
Straight 8.66 7.66 8.66

20. Weight Calculations
Section Weight
Curve (𝐿 𝑐 = 0.03 mi) 𝑊 𝑐 = 8.93+11.10+11.31
= 31.34
Tangent (𝐿 𝑇 = 0.09 mi) 𝑊 𝑇 = 8.93+11.10+8.66
= 28.69
Total (𝐿 = 0.12 mi) 𝑊 =
𝑊𝑐 𝐿 𝑐+𝑊 𝑇 𝐿 𝑇
𝐿
=29.35

21. Prioritize Locations
DI CO HWY ADT_CUR TRK_AADT FRM_DFO TO_DFO PAVED_WID length weight
1 75 BS0121D 516 8.9 1.68 1.8 20 0.12 29.35
1 75 BU0069B 1101 22.7 0.52 0.61 20 0.09 19.87
1 75 BU0069B 1101 22.7 0.61 0.96 20 0.35 19.87
1 194 BU0271D 1100 9 1.07 1.15 21 0.08 21.98
1 194 BU0271D 1100 9 1.64 1.65 20 0.01 13.87
1 92 BU0377B 2164 3.1 1.28 1.51 22 0.23 27.98
1 92 BU0377B 2164 3.1 1.51 4.29 22 2.78 28.41
1 92 BU0377B 2164 3.1 4.29 4.89 22 0.6 28.93
1 117 FM0006 2387 4.4 7.88 8.52 20 0.64 33.18

22. THANK YOU