Investigation of the Safety Effects of Edge and Centerline Markings on Narrow, Low-Volume Roads Lance Dougald Ben Cottrell Young-Jun Kweon In-Kyu Lim.

Investigation of the Safety Effects of Edge and Centerline Markings on Narrow, Low-Volume Roads

Lance Dougald

Ben Cottrell

Young-Jun Kweon

In-Kyu Lim

Outline

• Background• Purpose• What we did• What we found• Next steps

2

Pavement Markings

3

Introduction and Background

Evolving Problem – Increase in housing/retail development – Higher traffic volumes on nearby narrow roads

without markings– Thought: Improve safety with low cost

striping until higher cost design improvements could be implemented

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• VDOT Guidelines:– Centerlines

• ≥ 500 vpd, ≥18 ft width

– Edgelines• Primary and Secondary routes w/no curb & gutter• Minimum 20 ft width• Centerlines present

* where an engineering study indicates a need

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• MUTCD requirements:– Centerlines

• Urban arterials and collectors ≥ 20 ft width,

ADT ≥ 6,000 vpd (recommended ≥ 4,000)• All two-way streets with 3+ traffic lanes

– Edgelines• All freeways and expressways• Rural arterials ≥ 20 ft width, ADT ≥ 6,000 vpd

(recommended ≥ 3,000)

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Purpose and Scope

• Initially: to develop guidelines for marking edge and centerlines on low volume roads (≤ 3,000 vpd and 16-20 ft wide pavement)

• Two phase process– Phase I: investigate safety effectiveness of

markings using cross-sectional crash data– Phase II: before/after pilot study of edge and

centerline applications at candidate sites and B/C analysis.

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Methods

1. Conduct literature review (focusing on rural/suburban low volume roads)

2. Obtain information from other state DOTs

3. Develop inventory of current edge and centerline markings and database of crash history on narrow roads

4. Perform crash analysis (5 years of data – width, AADT, and presence of pavement markings) [cross-sectional analysis]

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Lit Review and Survey Results

• Variability found in past research– Crashes– Speed– Lateral positioning

• Variability in state DOT practices/policies– Majority follow MUTCD – Lower width/ADT thresholds from states that

maintain secondary road system

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Safety Impact of Edgelines on Rural Two-Lane Highways in Texas

• A before/after comparison study found edgelines reduced accident frequency up to 26%

• highest safety impacts on curved roadways with lane widths of 9-10 ft

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Benefit-Cost Analysis of Lane Marking

• paint costs $0.04 /linear-ft in rural areas and $0.07/linear-ft in urban areas

• existing longitudinal pavement markings reduce crashes by 21%

• edgelines on rural two-lane highways reduce crashes by 8 %

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Lure of Low Cost Markings

Using $0.07 per linear-ft:• $740 per mile centerlines • $1,480 per mile center and edgelines

VDOT HSIP average crash values• PDO: $9,000 B/C=6/1• Injury :$55,000-$275,000 B/C=37/1-

185/1 • Fatal :$5,000,000 B/C=33,784/1

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Kentucky DOT Guidelines

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Use of Edge Line Markings on Rural Two Lane Highways. 2008.

Pavement Width (ft)

Lane Width (ft)

Centerline EdgelinePaved

Shoulder Width (ft)

28 12 Yes Yes 2

27 12 Yes Yes 1.5

26 11 Yes Yes 2

25 11 Yes Yes 1.5

24 11 Yes Yes 123 10 Yes Yes 1.5

22 10 Yes Yes 1

21 9 Yes Yes 1.5

20 9 Yes Yes 1

19 8 Yes No 1.5

18 8 Yes No 1

17 7.5 No Yes 1

16 7 No Yes 1

15 6.5 No Yes 1

14 6 No Yes 1

State DOTs’ actions to increasing volumes on narrow roads

• Wyoming adds centerlines• Delaware was under pressure in two

counties to establish a low AADT criterion for centerlines

• Oregon adds edgelines if there are documented safety problems

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Inventory/Crash History

• HTRIS – 3 subsystems– Roadway Inventory (200,000 segments)– Accident/Crash (FR-300)– Traffic Monitoring System (CCS)

• 2004-2008 Crash Data– Eligible narrow and low volume segments– Presence of pavement markings (Google)

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HTRIS

RDISubsystem

Select segmentsmaintained in2004 - 2008

2004 RDI2005 RDI2006 RDI2007 RDI2008 RDI

Select segmentsTwo-lane, Two way

& Undivided

Select segmentspavement width

16ft - 20ft

TMSSubsystem

Select segments with AADT

1 - 3,000 veh.

Select segments onPrimary & Secondary

2004 TMS2005 TMS2006 TMS2007 TMS2008 TMS

ACCSubsystem

Compile RDI, TMS and ACC

data

Select segments with crashes in

2004 - 2008

AddMarking Inventory

2004 ACC2005 ACC2006 ACC2007 ACC2008 ACC

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Step 9

Join TMS to RDI

Join ACCto RDI

Step 10

Number of Lanes & Facility

Type

Route System

Pavement Width (ft)

Length (mi)

Total Crash

Frequency2004-2008

Two-lane

Undivided

Primary 16 20 6617 11 818 162 53619 68 21820 1,456 5,182

Secondary 16 122 25217 9 1218 351 32719 32 4020 285 166

Total 2,516 6,807

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Inventory/Crash History

• Matrix:– Pavement width (16’,18’,20’)– AADT band (<500, 501-3000)– Presence edge/centerlines– Number/length of segments– Crashes

• Total• Road Departure• Density

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Road Sections by Two AADT Bands and Presence of Pavement Markings

AADT Bands Centerline Edgeline Number of

SegmentsLength (miles)

≤ 500No

No 1,910 496Yes 12 6

YesNo 27 25Yes 232 194

501-3,000No

No 171 40Yes 6 3

YesNo 212 88Yes 2,227 1,180

Total 4,797 2,033

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No Markings and Edgelines Only

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Centerlines Only and Both Markings

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Crash Analysis

Question:

Are narrow roads with pavement markings safer than those without pavement markings?

• Compared roads with:– No markings– Centerline markings only– Edge-line markings only – Edge and centerline markings

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Crash Analysis

ANOVA:• Developed individual models for widths:

– 16’, 18’, 20’• Crash frequency (# of crashes)• Crash density (crashes/mile)• Crash rate (crashes/mile/vehicles)

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Number of segments and marking presence

Number of Segments EdgelinesAbsent Present

Centerlines Absent 2,081 18Present 239 2,459

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Crash frequency and marking presence

Crash Frequency(5-year crashes per

segment)

EdgelinesAbsent Present

Centerlines Absent 0.13 0.28Present 1.43 2.03

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Crash density and marking presence

Crash Density(5-year crashes per 0.5

mile)



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Crash Rate by marking presence

Crash Rate(5-year crashes per 0.5 mile per 1,000 vehicles)



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Number of segments by marking presence and pavement widthNumber of Segments Edgelines

Absent Present

16 feet Centerlines Absent 118 4Present 21 56



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Crash frequency by marking presence and pavement width

Crash Frequency(5-year crashes per

segment)


16 feet Centerlines Absent 0.42 0.25Present 2.62 2.66



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Crash rate by marking presence and pavement width

Crash Rate(5-year crashes per 0.5 mile

per 1,000 vehicles)





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Crash Analysis Results

ANOVA:• No statistical difference found for crash

frequency, density, and rate for each of the 4 marking scenarios

• Shortcoming: accounting for AADT, segment length

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Safety Performance Function (SPF)

A safety performance function (SPF) is an equation used to predict the average number of crashes per year at a location as a function of exposure and, in some cases, roadway or intersection characteristics (e.g., number of lanes, traffic control, or median type)

SPF estimated by the negative binomial model

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Crash Analysis

• Separate SPFs developed for 4 cases:• No lines present • Centerlines only• Edgelines only• Both lines present

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Crash Analysis• SPF results

• 3 segment groups appear different

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0

1

2

3

4

5

6

7

8

0 500 1,000 1,500 2,000 2,500 3,000

5-Y

ear

Cra

sh F

requ

ency

per

0.5

Mile

AADT

Crash Analysis• SPF results for 95% upper limit

• However, 3 curves are statistically identical

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0

2

4

6

8

10

12

14

16

0 500 1,000 1,500 2,000 2,500 3,000

5-Y

ear

Cra

sh F

requ

ency

per

0.5

Mile

AADT

Study sites vs all VDOT roads

no. road milesno. crashes 2004-2008

study sites 2,033 4,797VDOT roads 60,066 251,609% 3.4% 1.9%

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Pavement Marking Inventory

• how districts maintain a pavement marking inventory in terms of software, format, data quality and frequency of updating the inventory vary

• 2 districts did not have an inventory for these roads

• a uniform, up to date pavement marking inventory may have value

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Discussion: Perspectives

• HJR 243:– “the Virginia Department of Transportation be

requested to revise its standards for the provision of centerline pavement markings to include all appropriate secondary roads having a pavement width of 18 feet or more where official traffic counts indicate a minimum of 500 vpd.”

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Discussion: Perspectives

• The term “appropriate” may allow for guidance to be developed on what roads to mark and how to mark them

• Flexibility in HJR 243 to mark more roads? Mark fewer roads?

• Interpretation on the word “appropriate” is needed

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Limitations

• Before/after Empirical Bayes study ideal– Select and mark roads then wait for after data– Low number of crashes typical– Large number of road sections = impractical

• Driver’s behavior not addressed– Exploratory study utilizing data from VTTI’s

naturalistic driving study

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Conclusions

• High variability exists in state DOT practices for installing pavement markings on narrow roads

• Based on cross-sectional analysis of crash frequency, density, rate, and SPF prediction, there appears to be no statistical difference between segments with and without centerlines and/or edgelines

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Recommendations

1. VDOT’s Traffic Engineering Div. should consider developing a statewide process for a pavement marking inventory.

2. VDOT’s TED should consider asking the Office of the Attorney General for an interpretation/opinion of the term “appropriate” in HJR 243.

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Recommendations

3. VCTIR staff should consider an exploratory study to determine if data from VTTI’s naturalistic driving study may be used to evaluate driver behavior on narrow roads with and without centerlines and/or edgelines.

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Investigation of the Safety Effects of Edge and Centerline Markings on Narrow, Low-Volume Roads

http://www.virginiadot.org/vtrc/main/online_reports/pdf/14-r3.pdf

http://www.virginiadot.org/vtrc/main/online_reports/pdf/14-r3.pdf

Investigation of the Safety Effects of Edge and Centerline Markings on Narrow, Low-Volume Roads Lance Dougald Ben Cottrell Young-Jun Kweon In-Kyu Lim.

Documents

ft width edgelines primary

ft width centerlines

centerline markings

ft wide pavement

5noyes1 146noyes1 slide

kyu lim slide

presence of pavement

lure of low cost markings