data-driven safety analysis

Data-Driven Safety Analysis

MPO-COG Conference

February 4-5, 2019

An FHWA Every Day Counts Innovation

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1034

0

200

400

600

800

1000

1200

SC Traffic Deaths, 1938-2018

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47%

44% 43%

35% 32%

27% 27%

22%

18% 15%

13%

9% 9%

6% 5% 2% 1%

0%

10%

20%

30%

40%

50%

So what do you think

are causing the most

traffic crashes/deaths?

Top Crash Types, 2013-2017

Fatal and severe injury crashes

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47%

44% 43%

35% 32%

27% 27%

22%

18% 15%

13%

9% 9%

6% 5% 2% 1%

0%

10%

20%

30%

40%

50%Top Crash Types, 2013-2017

Fatal and severe injury crashes

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• Goal: Integrate safety performance into ALL transportation investment

decisions

Source: FHWA

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Foundation • Highway Safety Manual

Source: AASHTO

• Highway Capacity Manual

Source: Transportation Research Board

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Data-Driven Safety Analysis Defined

• The application of the latest evidence-based tools and approaches to

safety analysis

• Provides reliable estimates of an existing or proposed roadway’s

expected safety performance

• Helps agencies quantify the safety impacts of transportation

decisions, similar to the way agencies quantify:

• Traffic growth

• Environmental impacts

• Traffic operations

• Pavement life

• Construction costs Source: FHWA

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Scenario:

City had identified six candidate intersections

for rehabilitation of pedestrian facilities;

however, the city needs to narrow the list to

only three of the sites. Expected

improvements include replacing/widening

sidewalks and installing/updating crosswalks.

Task:

Where can limited funding be most

effectively spent?

Data-Driven Safety Analysis Defined Simplified

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What kind of information might you need

about the six intersections?

• Number of crashes (total & pedestrian)

• Traffic control

• AADT

• Presence of sidewalks/

crossings

• More?


Intersection

Number

Number of Crashes

(Three Years)

Number of Crashes

(Average per Year)

F &SI

Pedestrian

Crashes

Total

Crashes

F &SI

Pedestrian

Crashes

Total

Crashes

1 12 144 4 48

2 6 141 2 47

3 12 99 4 33

4 18 99 6 33

5 9 150 3 50

6 12 96 4 32

Average 11.5 121.5 3.8 40.5

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Intersection

Number

F &SI Pedestrian

Crashes Total Crashes

Pedestrian

Proportion of

Total Crashes

Ranking by

Ped Crash

Frequency

1 4 48 0.08 2

2 2 47 0.04 6

3 4 33 0.12 2

4 6 33 0.18 1

5 3 50 0.06 5

6 4 32 0.13 2

Total 23 243 N/A N/A

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Intersection

Number

F &SI Pedestrian

Crashes Total Crashes

Pedestrian

Proportion of

Total Crashes

Ranking by

Ped Crash

Frequency

1 4 48 0.08 2

2 2 47 0.04 6

3 4 33 0.12 2

4 6 33 0.18 1

5 3 50 0.06 5

6 4 32 0.13 2

Total 23 243 N/A N/A

Threshold proportion 23/243=0.09; any pedestrian proportion of total crashes greater than

0.09 merit consideration, based on this performance measure.

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What is this road’s

safety performance?

Top 3 Questions:

1. How many crashes?

2. Is that bad?

3. What can we do about it?



Crash Type Average

Crashes/Year

Total 48

Fatal & SI 15

Ped/Bike Related F & SI 2

Rearend 10

Right Angle 20

Top 3 Questions:


Top 3 Questions:


2. Is that bad?


Crash Type Average

Crashes/Year

Actual Predicted

Total Collisions 48 45

The number of crashes can be predicted using a Safety Performance Function (SPF) -> an equation; function of exposure and roadway or intersection characteristics (e.g. # of lanes, traffic control, AADT)

Top 3 Questions:


2. Is that bad?

3. What can we do about it?

• Crash modification factors & alternatives analysis!!!


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All three of these meet design standards…

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45 fatal and injury crashes/year 110 fatal & injury crashes/year 65 fatal & injury crashes/year

Alt 2 Alt 1 No-Build

but DDSA tells us they would perform very differently

from a safety perspective.

Source: CH2MHILL

An illustration of DDSA

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110 fatal & injury crashes/year

Example: TN DOT –

Communicating Alternatives TN Corridor Project

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Example: TN DOT –


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Example: TN DOT –


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Example: TN DOT –


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Where can DDSA be applied in the Project

Development Process?

Source: FHWA

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How can DDSA be applied in the Planning Process?

DDSA tools can be applied to help identify which roadways aren’t

performing as they should and determine the scope and need of

potential projects.

1. System level planning – Network Screening

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjljPSx5dneAhUE1lMKHQCjAhUQjRx6BAgBEAU&url=https://www.audiencetools.io/blog/event-marketing-data-analytics/&psig=AOvVaw3GjLOXEHCby7VgLoJ4XWhG&ust=1542487889523076

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DDSA tools can be applied to help identify which roadways aren’t

performing as they should and determine the scope and need of

potential projects.

1. System level planning – Network Screening

2. Project level planning – Establish Scope

i. Assess the performance of the site

• Condition/status of pavement, structures, congestion, safety, etc.

ii. Propose improvements

iii. Determine necessary funding and schedule

How can DDSA be applied in the Planning Process?

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Safety Score as part of the Project Prioritizations

• Historical safety performance at a potential project location

• Coordinate with HSIP screening results

• Expand to include high-level safety B/C ratio for project concepts

• Requires development of safety benefit factors (or planning level CMFs)

• Coordinate State-level CMF list(s) with preconstruction, traffic

engineering, and safety

Planning Opportunities

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Project Feasibility Report

• Purpose and Need

• Develop guidelines for when (and when not) to and how to include safety in

project purpose and need

• Scale and Scope of Project

• Determine if safety features should be included in scope using historical

performance and crash patterns

• Historical safety performance + planning-level CMFs to determine return on

investment

Planning Opportunities

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• Shift from Nominal to Substantive Safety

• Move toward use of SPFs/CMFs in design decisions

• Safety is not all or nothing (e.g., minimum ramp spacing)

• Help RPGs, MPOs, COGs develop better projects

• Share network screening list

• Engage during scoping (with planning)

Preconstruction Opportunities

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• Share network screening list

• Planning (Purpose and Need)

• MPOs/COGs (assist decision making)

• Identify cost-effective countermeasures (systemic)

• Support safety analysis

• Planning-level CMFs

• Shortlist of CMFs from the CMF Clearinghouse

• Calibrated SPFs for use in predictive analysis

• Tools to facilitate analysis (IHSDM, spreadsheets, etc.)

Safety Management Process

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DDSA tools can predict the number and severity of crashes for each

project alternative, allowing safety performance to be considered along

with other project criteria

Integrating Safety into NEPA Process when:

1. Safety is included in the Purpose and Need

2. Projects that claim a safety benefit

3. Projects where there could be a substantial difference in safety for

the alternatives being considered

4. Projects with existing safety issues

Appling DDSA to Alternatives Analysis

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• County maintained road

• Provides access to several commercial developments

• Located approx. 600 feet from the I-20 WB off ramp

• Access to Wall Street

McDonalds, Exxon

&Tigershop

Fatz Cafe

Comfort Inn & Suites

BP Gas

Mobil Gas

Waffle

House

Holiday Inn

Express

Alternative Analysis Example

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Based on 5 years worth of recent crash data, there have been 36 crashes reported at this intersection, with 50 percent resulting in an injury to one or more occupants.

Alternative Analysis Example – Crash Statistics

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RCUT Traffic Signal

Assumed Cost= $750,000 $750,000

B/C Ratio=

Net Annual

Benefit=


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RCUT – Restricted Crossing U-Turn

Source: Wisconsin DOT

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RCUT Traffic Signal

Assumed Cost= $750,000 $750,000

B/C Ratio= 4.69 .35

Net Annual

Benefit=


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RCUT Traffic Signal

Assumed Cost= $750,000 $750,000

B/C Ratio= 4.69 .35

Net Annual

Benefit= $153,500 ($27,000)


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Example: AZ DOT Analysis of Design Criteria

Alternative Improvements Included:

• Widening to 5 ft shoulders

• Widening to 8 ft shoulders

(MP 441 to 466)

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Credit: Arizona DOT

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Plot of Geometric Features and Expected Crashes

Example – Arizona DOT

Credit: Arizona DOT

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Crash Prediction Results


• Safety Analysis:

• Model was un-calibrated as used (not necessary for comparative

alternatives analysis)

• Alternative B (8-ft shoulders) would reduce crashes by 4 percent more than

Alternative A (5-ft shoulders)

Credit: Arizona DOT

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• Economic analysis:

• Although Alternative B (8-ft shoulders) could provide the greater

benefit in reduction in fatal and injury crashes, Alternative A (5-ft

shoulders) would provide the greater return on investment and

was selected as the preferred alternative.

Credit: Arizona DOT

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DDSA & Target Setting

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Performance Targets National Goals

1. Safety

2. Infrastructure Condition

3. Congestion Reduction

4. System Reliability

5. Freight Mvmt & Economic Vitality

6. Environmental Sustainability

7. Reduced Project Delivery Delays

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1. Safety







Measures

Number and Rate of Traffic Fatalities

Number and Rate of Serious Injuries

Number of non-motorized user

fatalities and serious injuries

combined

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1. Safety







Measures

Number and Rate of Traffic Fatalities

Number and Rate of Serious Injuries

Number of non-motorized user

fatalities and serious injuries

combined

Measures common the

SCDPS/Highway Safety Office

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Performance Targets Timeline

April 2018 – safety stakeholders

coordinate on setting 2015-2019

HSIP targets

May 2018 – MPO/COG meeting at

DOT; draft safety targets were

presented

DEADLINES

December 2019 – significant

progress determination on 2014-2018

targets

Deadlines

• State Highway Safety Offices report 3 identical HSIP targets in the HSP to NHTSA

July 1, 2018

• State DOT’s report 2015-2019 HSIP targets in the HSIP Annual Report to FHWA

August 31, 2018

• Last day for MPOs to establish 2015-2019 Target

February 27, 2019

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Performance Measure

5-year Rolling Averages

2012-2016

Baseline

Performance

2014-2018

Target

2014-2018

Preliminary

Performance

Number of Fatalities 890 970 969

Fatality Rate 1.75 1.81 1.81

Number of Serious

Injuries 3194 3067 2952

Serious Injury Rate 6.3 5.71 5.54

Number of Non-motorized

Fatalities and Serious

Injuries

376 371 380

South Carolina

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Performance Measure


2013-2017

Baseline

Performance

2015-2019

Target

Number of Fatalities 915 988

Fatality Rate 1.75 1.79

Number of Serious Injuries 3088 2986

Serious Injury Rate 5.94 5.42

Number of Non-motorized Fatalities

and Serious Injuries 381 380

South Carolina

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Performance Measure


2012-2016

Baseline

Performance

2014-2018

Target

2013-2017

Baseline

Performance

2015-2019

Target

Number of Fatalities 890 970 915 988

Fatality Rate 1.75 1.81 1.75 1.79

Number of Serious

Injuries 3194 3067 3088 2986

Serious Injury Rate 6.3 5.71 5.94 5.42

Number of Non-motorized

Fatalities and Serious

Injuries

376 371 380 380

South Carolina

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Performance Targets Timeline

• April 2019 – safety stakeholders

coordinate on setting 2016-2020

HSIP targets

• May 2019 – provide draft safety

targets to MPO/COG

• DEADLINES

• December 2019 – significant

progress determination on 2014-

2018 targets

Deadlines

• Last day for MPOs to establish 2015-2019 Target

February 27, 2019

• State Highway Safety Offices report 3 identical HSIP targets in the HSP to NHTSA

July 1, 2019

• State DOT’s report 2016-2020 HSIP targets in the HSIP Annual Report to FHWA

August 31, 2019

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Current or Planned Projects

• Review crash data for possible countermeasures

• Identify scope items that are the most cost effective

• Calculate possible reductions in fatalities/serious injuries

• Set achievable, data-driven, targets

How can DDSA be applied to the Safety Target

Setting Process?

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Performance Target Resources • https://safety.fhwa.dot.gov/hsip/spm/

• http://www.cmfclearinghouse.org/

https://safety.fhwa.dot.gov/hsip/spm/

https://safety.fhwa.dot.gov/hsip/spm/

http://www.cmfclearinghouse.org/

http://www.cmfclearinghouse.org/

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Target Achievement by State https://safety.fhwa.dot.gov/hsip/spm/state_safety_targets/

https://safety.fhwa.dot.gov/hsip/spm/state_safety_targets/




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FHWA Consultation

• Review current process and any documentation

• Interviews with SCDOT

• Provide recommendations

Safety Matrix

Conduct or review safety analysis on new (and current) projects

What’s next?

data-driven safety analysis

Documents