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

1. 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

2. Outline • Background • Purpose • What we did • What we found • Next steps

3. Pavement Markings

4. 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

5. Introduction and Background • 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

6. Introduction and Background • 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)

7. 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.

8. Methods • Conduct literature review (focusing on rural/suburban low volume roads) • Obtain information from other state DOTs • Develop inventory of current edge and centerline markings and database of crash history on narrow roads • Perform crash analysis (5 years of data – width, AADT, and presence of pavement markings) [cross-sectional analysis]

9. 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

10. 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

11. 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 %

12. 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

13. Kentucky DOT Guidelines Use of Edge Line Markings on Rural Two Lane Highways. 2008.

15. 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

16. 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)

19. 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

20. Road Sections by Two AADT Bands and Presence of Pavement Markings

21. No Markings and Edgelines Only

22. Centerlines Only and Both Markings

24. 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

25. Crash Analysis ANOVA: • Developed individual models for widths: • 16’, 18’, 20’ • Crash frequency (# of crashes) • Crash density (crashes/mile) • Crash rate (crashes/mile/vehicles)

26. Number of segments and marking presence

27. Crash frequency and marking presence

28. Crash density and marking presence

29. Crash Rate by marking presence

30. Number of segments by marking presence and pavement width

31. Crash frequency by marking presence and pavement width

32. Crash rate by marking presence and pavement width

33. 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

34. 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

35. Crash Analysis • Separate SPFs developed for 4 cases: • No lines present • Centerlines only • Edgelines only • Both lines present

36. Crash Analysis • SPF results • 3 segment groups appear different

37. Crash Analysis • SPF results for 95% upper limit • However, 3 curves are statistically identical

38. Study sites vs all VDOT roads

39. 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

40. 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 appropriatesecondary roads having a pavement width of 18 feet or more where official traffic counts indicate a minimum of 500 vpd.”

41. 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

42. Limitations • Before/after Empirical Bayesstudy 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

43. 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

44. Recommendations • VDOT’s Traffic Engineering Div. should consider developing a statewide process for a pavement marking inventory. • VDOT’s TED should consider asking the Office of the Attorney General for an interpretation/opinion of the term “appropriate” in HJR 243.

45. 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.

46. 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