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Element 1: 4-Step Project Selection Process. Element 1: The Systemic Safety Project Selection Process. Objective. Identify risk factors commonly associated with target crash type(s) experienced across a system. Suggest a focus on severe crashes (fatal + serious injury)

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element 1 4 step project selection process
Element 1: 4-Step Project Selection Process

Element 1: The Systemic Safety Project Selection Process

objective
Objective
  • Identify risk factors commonly associated with target crash type(s) experienced across a system.
  • Suggest a focus on severe crashes (fatal + serious injury)
    • Consistent with national safety practices
    • May minimize effort and needed resources

Element 1, Step 1: Identify Target Crash Types & Risk Factors

outcome
Outcome
  • Gain an understanding of the systemic program’s focus
    • Type of Crash
    • Facility Type (i.e., location type)
    • Risk Factors

Element 1, Step 1: Identify Target Crash Types & Risk Factors

recommended minimum data
Recommended Minimum Data
  • Crashes by system (state and local)
  • Crash type (road departure, right angle, head-on rear end, turning, etc.)
  • Facility type (freeway, expressway and conventional)
  • Physical crash location description (urban/rural, intersection/segment, tangent/curve, topography, etc.)
  • Description of location (topography, intersection elements, segment elements)

Element 1, Step 1: Identify Target Crash Types & Risk Factors

potentially useful data i e risk factors
Potentially Useful Data(i.e., Risk Factors)
  • Traffic volumes
  • Some Roadway Features
    • Number of lanes
    • Shoulder type/width
    • Road edge features/quality
    • Number/type of access
    • Radius of horizontal curves
    • Density of horizontal curves
    • Speed limit
    • Medians
  • Some Intersection Features
    • Number of approaches
    • Skew
    • Proximity to horizontal/vertical curves
    • Number of approach lanes
    • Signal timing
    • Proximity to railroad crossing
    • Traffic control devices
    • Presence of street lighting
    • Presence of commercial developments

Element 1, Step 1: Identify Target Crash Types & Risk Factors

element 1 step 1
Element 1: Step 1

Element 1, Step 1: Identify Target Crash Types & Risk Factors

element 1 step 1 task 1 select focus crash type s
Element 1: Step 1, Task 1Select Focus Crash Type(s)

Purpose:

  • Identify the greatest potential to reduce fatalities and severe injuries.

Suggestion:

  • Identify crash type(s) representing the greatest number of severe crashes across system.

Element 1: Step 1, Task 1

element 1 step 1 task 1 select focus crash type s1
Element 1: Step 1, Task 1Select Focus Crash Type(s)
  • Why is it important to select a focus crash type(s)?
  • There is no single countermeasure that is effective at addressing all crash types. Identifying a focus crash type(s) will help narrow down the list of countermeasures.
  • Q:
  • A:

Element 1: Step 1, Task 1

element 1 step 1 task 1 select focus crash type s2
Element 1: Step 1, Task 1Select Focus Crash Type(s)

Resources:

  • State or regional SHSP
    • AASHTO’s 22 Emphasis Areas
  • Roadway Departure or Intersection Safety Implementation Plans
  • Other applicable safety plans
  • Statewide and regional crash data

Element 1: Step 1, Task 1

element 1 step 1 task 1 select focus crash type s3
Element 1: Step 1, Task 1Select Focus Crash Type(s)

Process:

  • Reference emphasis areas defined in approved safety plans (State SHSP).
  • Stratify crash data into emphasis areas.
  • Select focus crash type(s):
    • Emphasis areas with highest frequency crashes
    • Priority order of emphasis areas in plans
    • Agency preferences

Element 1: Step 1, Task 1

statewide data by safety emphasis area
Statewide Data by Safety Emphasis Area

Illustration: Jurisdictioncan make a difference

Element 1: Step 1, Task 1

region data by safety emphasis area
Region Data by Safety Emphasis Area

Illustration: Consider impactof geography & topography

Element 1: Step 1, Task 1

element 1 step 1 task 1 select focus crash type s4
Element 1: Step 1, Task 1Select Focus Crash Type(s)

Possible Challenges for Thurston County:

  • Relatively few severe crashes?…difficult to identify focus crash type(s)
  • Urban and rural areas have distinctly different crash patterns?

Element 1: Step 1, Task 1

element 1 step 1 task 2 select focus facilities
Element 1: Step 1, Task 2Select Focus Facilities

Purpose:

  • Determine locations on roadway network where focus crashes occur most frequently.

Element 1: Step 1, Task 2

element 1 step 1 task 2 select focus facilities1
Element 1: Step 1, Task 2 Select Focus Facilities
  • Why is it important to select focus facilities?
  • There is no single countermeasure that is appropriate for all situations. Identifying a focus facility type will help narrow down the list of countermeasures.
  • Q:
  • A:

Element 1: Step 1, Task 2

element 1 step 1 task 2 select focus facilities2
Element 1: Step 1, Task 2Select Focus Facilities

Resources:

  • Roadway Departure or Intersection Safety Implementation Plans
  • Statewide and regional crash data

Process:

  • Develop crash tree diagram.
  • Utilize diagram to identify and select focus facilities.

Element 1: Step 1, Task 2

greater minnesota crash tree diagram
Greater Minnesota Crash Tree Diagram

Source: MnCMAT Crash Data, 2006-2010

Severe is fatal and serious injury crashes (K+A).

5 Year Crashes

156,182

4,902

-Region’s 1, 2, 3, 4, 6, 7, and 8 – NO Metro

Example

All – %

Severe – %

CSAH/CR

36,716 – 24%

1,963 – 40%

State System

70,808 – 45%

2,000 – 41%

City, Twnshp, Other

48,658 – 31%

939 – 19%

Urban

14,086 – 38%

337 – 17%

Rural

22,630 – 62%

1,626 – 83%

Not Animal

18,616 – 82%

1,566 – 96%

Animal

4,009 – 18%

60 – 4%

Unknown/Other

1,577 – 11%

17 – 5%

Not Inters-Related

5,177 – 37%

175 – 52%

Inters-Related

7,332 – 52%

145 – 43%

Unknown/Other

1,276 – 7%

61 – 4%

Inters-Related

5,487 – 29%

463 – 30%

Not Inters-Related

11,849 – 64%

1,042 –66%

Run Off Road – 1,202 (23%), 69 (39%)

Head On – 366 (7%), 27 (15%)

“Other” – 540 (10%), 25 (14%)

Rear End – 1,336 (26%), 17 (10%)

Other/Unknown

2,600 – 47%

228 – 49%

Signalized

209 – 4%

4 – 1%

All Way Stop

164 – 3%

15 – 3%

Thru-Stop

2,511 – 46%

216 – 47%

Head On, SS Opp.

751 – 6%

132 – 13%

Run off Road

7,891 – 67%

675 – 65%

Signalized

2,308 – 31%

32 – 22%

All Way Stop

445 – 6%

5 – 3%

Thru-Stop

2,697 – 37%

65 – 45%

Other/Unknown

1,881 – 26%

43 – 30%

Run Off Road – 999 (38%), 95 (42%)

Right Angle – 268 (10%), 39 (17%)

“Other” – 303 (12%), 29 (13%)

Head On – 112 (4%), 21 (9%)

On Curve

247 – 33%

46 – 35%

On Curve

3,222 – 40%

339 – 50%

Right Angle – 633 (27%), 15 (47%)

Rear End – 799 (35%), 5 (16%)

Left Turn – 375 (16%), 5 (16%)

Head On – 100 (4%), 4 (13%)

Right Angle – 1,268 (47%), 37 (86%)

“Other” – 252 (9%), 9 (21%)

Left Turn – 268 (10%), 4 (9%)

Rear End – 333 (12%), 3 (7%)

Right Angle – 849 (34%), 122 (56%)

“Other” – 464 (18%), 33 (15%)

Run Off Road – 342 (14%), 21 (10%)

Left Turn – 184 (7%), 10 (5%)

Element 1: Step 1, Task 2

element 1 step 1 task 2 select focus facilities3
Element 1: Step 1, Task 2Select Focus Facilities
  • Suggest Minimum Crash Tree Combinations:
    • Location (urban / rural)
    • Ownership (state and local)
    • Segment or intersection
    • Segment type (freeway, multilane, two-lane, one-way)
    • Intersection control type (signal, stop, yield)
  • Additional Crash Tree Combinations:
    • Tangent or curve
    • High- or low-speed
    • Presence of street lighting
    • District or regions

Element 1: Step 1, Task 2

element 1 step 1 task 3 identify and evaluate risk factors
Element 1: Step 1, Task 3Identify and Evaluate Risk Factors

Purpose:

Document the most common characteristics of the crash locations to further define the facility types selected from the crash tree in Step 1, Task 2.

Element 1: Step 1, Task 3

element 1 step 1 task 3 identify and evaluate risk factors1
Element 1: Step 1, Task 3Identify and Evaluate Risk Factors
  • Why are risk factors needed?
  • Risk factors help differentiate which locations may have the greatest potential for a future focus crash type.
  • These locations become the priority for where to deploy countermeasures.
  • Q:
  • A:

Element 1: Step 1, Task 3

element 1 step 1 task 3 identify and evaluate risk factors2
Element 1: Step 1, Task 3Identify and Evaluate Risk Factors

Resources:

  • Crash data at statewide and regional levels
  • Road and intersection data
  • Highway Safety Manual
  • FHWA’s Crash Modification Factor Clearinghouse
  • Published research documenting the effectiveness of strategies

Element 1: Step 1, Task 3

element 1 step 1 task 3 identify and evaluate risk factors3
Element 1: Step 1, Task 3Identify and Evaluate Risk Factors

Process:

  • Determine potential risk factors considering:
    • Ability to indicate greater potential for a future severe focus crash type
    • Availability of data element in existing databases or the ability to quickly gather data if not already available
    • Quality of data element if contained in existing databases
    • Applicability of data element to focus crash type and facility type

Element 1: Step 1, Task 3

element 1 step 1 task 3 identify and evaluate risk factors4
Element 1: Step 1, Task 3Identify and Evaluate Risk Factors

Process:

2. Evaluate potential risk factors for a relationship to future crash potential:

  • Formal statistical analysis to determine if risk factor associated with crash frequency
  • Compare proportions…proportion of all locations with the characteristic versus proportion severe crash locations with (descriptive statistics)
  • Review published research to identify Crash Modification Factors

3. Select risk factors.

Element 1: Step 1, Task 3

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