systemic approach to safety in texas · 2017. 1. 4. · systemic approach to safety in texas ......
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Systemic Approach to
Safety in Texas Srinivas Reddy Geedipally, PhD, PE
June 9, 2015
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
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”?
Systemic Project Selection Tool
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
Systemic Widening Program
Head-On Single Vehicle Run Off Road
K & A Crashes
SVROR Crashes Single Vehicle
8439
Urban758 (11%)
Rural6030 (89%)
Overturned2485 (37%)
Fixed Object4138 (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 OnlyTwo-lane Two-way Highways
Source: TxDOT CRIS, 2009-2013
Other/Unknown165 (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 Width18-20: 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 Roadway1651 (20%)
ROR6788 (80%)
Fatal - 2167 (26%)Incap. injury- 6272 (74%)
ADT0-399: 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%)
Head-on Crashes Head-on
2023
Fatal and Incapacitating Injury Crashes OnlyTwo-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%)
ADT0-399: 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%)
Urban358 (18%)
Rural1665 (82%)
Fatal - 1015 (50%)Incap. injury- 1008 (50%)
Total Paved Width18-20: 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%)
Evaluate Risk Factors
Average Daily Traffic Highways are categorized into: Low volume: 400 < ADT <700 Moderate volume: 700 < ADT <1500 High volume: ADT > 1500
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
Perc
ent
Lane Width + Shoulder Width (ft)
LengthKA 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
Perc
ent
Lane Width + Shoulder Width (ft)
LengthKA Crashes
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%
Perc
ent
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%
Perc
ent
Truck Presence
Length
KA Crashes
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
Perc
ent
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
Perc
ent
Alignment
Length
KA Crashes
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%
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
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
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.
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
Practical Application
DFO = 1.68
DFO = 1.73
DFO = 1.76
DFO = 1.8
𝐿𝑐 = 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
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
Weight Calculations
Section Weight Curve (𝐿𝑐 = 0.03 mi) 𝑊𝑐 = 8.93+11.10+11.31
= 31.34 Tangent (𝐿𝑇 = 0.09 mi) 𝑊𝑇 = 8.93+11.10+8.66
= 28.69 Total (𝐿 = 0.12 mi) 𝑊 = 𝑊𝑐𝐿𝑐+𝑊𝑇𝐿𝑇
𝐿=29.35
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
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