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Highway Safety Improvement Program (HSIP) - Central Region Projects & Status

Kenai Peninsula Area

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PROJECT:

11CR2: Sterling Highway: Soldotna to Homer Hill Slow Vehicle Turnouts (SVT)

Description:

The Sterling Highway between Soldotna and Homer Hill is a two lane two-way highway designated as a rural principal arterial.

Existing Crash Patterns

Existing crash patterns for the 2004-2008 HSIP evaluation period were reviewed for the Seward Highway between Soldotna (MP97) and the top of Homer Hill (MP 169).  The following are crashes within this corridor by severity:

Sterling Highway: Soldotna to Homer Hill 2004-2008 Crashes

YEAR
Fatality
Incapacitating Injury
Non-Incapacitating or Possible Injury
Property Damage Only
GRAND TOTAL

2004

3

7

35

88

133

2005

1

8

34

91

134

2006

0

5

36

94

135

2007

2

8

29

79

118

2008

0

4

19

70

93

Grand Total

6

32

153

422

613

Prominent among these crashes, particularly those that result in a fatality, are the head-on crashes.  1/2 of the fatal crashes occurring between Soldotna and the top of Homer Hill were head-on crashes.  Although most head-on fatal crashes are not related to an intentional passing maneuver (less than 10%), those that do occur generate considerable attention and calls for highway improvements.

Roadway Uses & Passing Opportunities

The Sterling Highway between Soldotna and Homer Hill links Soldotna and areas north including Anchorage with the City of Homer, a significant fishing and recreational destination at the southern end of the Sterling Highway.  This portion of the Sterling Highway experiences large traffic and recreational use increases during the summer months with over 11% being recreational vehicles or delivery trucks.  Commercial vehicles make up over 14% of the total traffic volume with vehicles pulling trailers make up more than 30% of the total traffic on this segment.

2008 Average daily traffic volumes range from a high of 6000 at the Soldotna end to 4700 at the top of Homer Hill.  156-183% of the average daily traffic occurs in June, July and August, the highest travel months on this segment of the Sterling Highway.  Summer peaks in the vicinity of Anchor point have exceeded the average daily traffic volumes by more than double.

The mixture of lower speed “sightseeing”, RV and boat hauling drivers with the more aggressive weekend fishing trip driver causes conflict and results in driver impatience, inattention, excessive speed, improper passing, fatigue, etc.  This situation is more complex during the summer months when as many as 7,000 vehicles, with a significant percentage being slower RV’s and boat haulers, travel the Sterling Highway daily as opposed to between 2000-3000 during the winter months.

Following slower and larger vehicles traveling at less uniform speeds increases driver impatience and often results in increased reckless and aggressive driving and fatigue.  These are greater factors in head-on collisions than actual passing maneuvers.

There are no passing lanes and no officially designated slow vehicle turnouts between Soldotna and the top of Homer Hill.  Therefore, passing must be done in the opposing lane of travel.  Additional turnout and/or passing opportunities are needed to help accommodate the differing types of uses and resulting travel speeds on the Sterling Highway between Soldotna and Homer.

Proposed Mitigation

Suitable Locations for Slow Vehicle Turnouts (SVT)

To help mitigate the number of fatal and injury head on, passing and rear end crashes involving passing or attempting to get around slower and/or slowing traffic, driver fatigue and recklessness, we determined that slow vehicle turnouts (SVT) would be the best mitigation in the short term.  While passing lanes are desirable, there are few one mile or longer segments that do not involve wetlands, or that provide optimum grades and visibility.  Passing lanes would cost substantially more to construct as well as lengthening the project schedule by more than 3 years.

Locations for SVT were chosen following a field review of potential SVT locations on the Sterling Highway between Soldotna and the top of Homer Hill.  Locations for SVT were selected where:

  • they would provide the most benefit,

  • where sight distance is available for slow vehicles to reenter the highway,

  • at or near where crashes have occurred, at locations without driveway conflicts (unless turning lanes are provided)

  • there were no apparent environmental impacts, no right of way issues, little or no utility involvement, and

  • Where slow vehicle turnouts or passing lanes could be constructed with minimal roadway widening.

The Federal Highway Administration (FHWA) does not recommend mixing SVT’s and passing lanes on a segment, so SVT’s were chosen based on the above criteria.  The following locations were selected for SVT improvements:

SVT Locations:

  • Milepost 106 Northbound SVT Lane (extend existing turnout)

  • Milepost 106 Southbound SVT Lane (new SVT lane)

  • Milepost 116 Southbound SVT Lane (new SVT lane)

  • Milepost 116 Northbound SVT Lane (new SVT lane)

  • Milepost 123 Southbound SVT Lane (new SVT lane)

  • Milepost 123 Northbound SVT Lane (new SVT lane)

  • Milepost 131.4 Northbound SVT Lane (new SVT lane)

  • Milepost 131.4 Southbound SVT Lane (new SVT lane)

  • Milepost 133 Northbound SVT Lane (new SVT lane)

  • Milepost 142.5 Southbound SVT Lane (fill in and extend existing turnout)

  • Milepost 147 Northbound SVT (new SVT lane)

  • Milepost 150 Northbound SVT Lane (new SVT lane)

  • Milepost 151 Northbound SVT Lane (new SVT lane)

  • Milepost 159 Northbound SVT Lane (new SVT lane)

  • Milepost 162.5 Northbound SVT Lane (new SVT lane)

The Department is currently working on a project to reconstruct a portion of the Sterling Highway from Milepost 157-169.  The Sterling Highway: MP 157-169 Reconstruction-Anchor Point to Baycrest Hill Is currently scheduled for construction funding beginning in 2014.  If this project remains on the 2014 schedule, the two proposed SVT lanes at  Milepost 159 and 162.5 could be deleted from the HSIP project.

Proposed SVT lanes will be laid out in accordance with the SVT detail included in Chapter 11 of the Alaska DOT/PF Preconstruction Manual.  This detail is shown below.

Click for larger view

NCHRP Report 500, volume 4: A Guide for Addressing Head-On Collisions suggests a reduction factor of 40% for all fatal and injury crashes and a 30% reduction for total crashes through the installation of turnouts.  The report states that passing lanes are known to have downstream operational effects for between 3-8 miles and suggests there may also be downstream safety effects.  Our Department applies reduction factors for the length of the passing lane or turnout as well as for downstream operational effect distances for turnouts. The “Desktop Reference for Crash Reduction Factors”, Report FHWA-SA-07-015, September, 2007: provides reduction factors for flush median installation and the installation of additional lanes and their effect on head-on, rear end, right angle, run-off-the road and sideswipe crashes.

We used a 30% factor to estimate crash reduction for pullouts, and their downstream areas.  The upstream area for crash mitigation with SVT’s was defined by using the advance signing distance for SVT’s of 1000 feet in advance of the SVT entrance taper.

The downstream area for crash mitigation with SVT’s were defined by using the values given for a passing lane, assuming a passing lane 1 mile in length, and reducing the downstream effect to account for the shorter SVT lanes.  Assuming a 600 foot SVT lane and a factor of 1/5th the impact length of a passing lane for the downstream SVT effect, we used a value of 4000 feet for the downstream effect.  The SVT influence area used for this candidate project is depicted below.

Based on the roadway segments for SVT mitigation discussed above, we applied the reduction factor to the following areas and crash types:

Area

Crash Type

Between a point 1000’ in advance of the begin taper (location of advance SVT sign) and end taper points of proposed passing lanes/slow vehicle turnouts:

All crashes, including head-on, sideswipe passing and run off the road crashes in the direction of travel of the proposed SVT.  (Excludes Moose & Animal crashes)

4000’ downstream starting at the end taper point

All crashes, including head-on, sideswipe passing and run off the road crashes in the direction of travel of the proposed SVT.  (Excludes Moose & Animal crashes)

We applied the factor for 4000 feet downstream even though the NCHRP report does not include it in their estimate, because the purpose of turnouts is to relieve aggression, fatigue from following a slow moving vehicle, and passing pressure.  We feel that that relief would extend beyond the end of the SVT lane, just as the report indicates that the operational effect of a passing lane downstream is 3-8 miles. 

We used the 30% reduction factor noted in the NCHRP study rather than 40% for turnouts because it seems unlikely that turnouts would be more effective than passing lanes at relieving passing pressure.

Crashes susceptible to correction are summarized below:

Sterling Highway: Soldotna to Homer Hill Crashes Potentially Correctable by the Installation of SVT Lanes

YEAR

Fatality

Incapacitating Injury

Non-Incapacitating or Possible Injury

Property Damage Only

GRAND TOTAL

2004

2

0

1

10

13

2005

0

0

3

8

11

2006

0

1

1

0

2

2007
1
2
2
2

7

2008

0

0

2

1

4

Grand Total

3

3

10

21

37

Crashes in the analysis susceptible to correction through the installation of SVT lanes include the following:


YEAR

Fatality

Incapacitating Injury

Non-Incapacitating or Possible Injury

Property Damage Only

GRAND TOTAL

Vehicle-Run Off the Road

1

2

4

10

17

OTHER/ Unknown

 

 

1

4

5

Fixed Object

 

 

2

3

5

VEH-Head On Related

2

 

2

2

6

VEH - Passing Related

 

 

1

2

3

VEH - REAR END

 

1

 

 

1

Grand Total

3

3

10

21

37

The HSIP improvements should result in a reduction in head-on, rear end, and lane changing crashes on the Sterling Highway between Soldotna and Homer Hill.

This project is scheduled for construction in 2013.

Project Contact:

Kevin Jackson, P.E.
Alaska State Department of Transportation and Public Facilities (ADOT&PF)
907-269-0641

kevin.jackson@alaska.govsend email