Benefits of Center Line Rumble Strips on Rural 2-Lane Highways in Louisiana Xiaoduan Sun, Ph.D., P.E. University of Louisiana at Lafayette 2018 Louisiana Transportation Conference Baton Rouge, February 26, 2018
Rumble Strips Rumble strips, also known as sleeper lines, alert strips, audible lines, wake up calls, growlers, drift lines, and drunk bumps 2
How CLRS Helps 3
Applications Typical shoulder rumble strip installation Midlane rumble strip concept Typical centerline rumble strip installation Typical transverse rumble strip installation 4
Types of Rumble Strips Milled, applied to existing hardened asphalt or concrete roads. Rolled, applied to newly laid asphalt pavement while it is still warm and moldable. Formed, a corrugated form is pressed into fresh concrete. Raised, fastened to asphalt or concrete pavement and often with a reflector built into the edge. 5
Milled, applied to existing hardened asphalt pavement 6
Design Dimensions Typical milled rumble strip widths are 5 to 7 inches (C) with 12-inch spacing (E) and approximately 0.5 inch depth (D). A typical length is 12 to 16 inches (B). 7
Easy Construction 8
Project Motivation Year Fatalities Per 100,000 Population Fatalities Per 100,000 Licensed Drivers Fatalities Per 100,000 Registered Vehicles Fatality Rate U.S. Louisiana U.S. Louisiana U.S. Louisiana U.S. Louisiana Change between 1994 and 2014-34% -19% -34% -31% -44% -22% -38% -32% Destination Zero Deaths calls for all actions that can reduce traffic crashes (fatal, injury and PDO) 9
Rural 2-lane Centerline rumble strips (CLRS) Project About 20% of the fatal crashes were cross-centerline crashes (head-on + opposite direction sideswipe) on Louisiana rural two-lane highways. Since 2011, CLRS have been installed on 2,100 miles of rural two-lane highways in Louisiana. 10
Centerline Rumble Strips in Louisiana (rural 2-lane) Project District Length (mile) Construction Year(s) 737-92-0089 2 109.73 2011 737-93-0070 3 205.12 2011 737-94-0065 4 404.59 2010-2012 737-95-0043 5 257.22 2011 737-97-0048 7 229.47 2011-2012 737-98-0045 8 297.55 2011-2012 737-91-0037 58 195.07 2011 737-96-0085 61 186.86 2011-2012 737-90-0087 62 272.79 2011 Total 2,158.4 11
Data Collection and Verification CLRS from project list Verifying by GIS Verifying by Google map street view 12
Summary of Segments in Analysis District Length # of Control (mile) Sections Before Years After Years 2 68.15 10 2008-10 2012-14 3 171.75 31 2008-10 2012-14 4 367.13 43 2007-09 2013-15 5 240.87 36 2008-10 2012-14 7 215.81 27 2008-10 2013-15 8 277.54 40 2008-10 2013-15 58 185.56 29 2008-10 2012-14 61 142.58 26 2008-10 2013-15 62 195.94 39 2008-10 2012-14 Total 1,865.33 281 13
Crashes Before and After CLRS Installation Crashes Before After Percent Reduction Total crashes Crashes by severity 5,829 4,950 15.1% Fatal 141 97 31.2% Injury 2,516 1,960 22.1% PDO 3,172 2,893 8.8% 14
Changes in Traffic Volume? AADT Before After Minimum 240 188 Maximum 18,633 22,367 Mean 3,337 3,389 Crash Rate Before After Crashes per million miles traveled 1.04 0.88 15
Changes by Collision Type Manner of collision Before After Percent Reduction Non-collision 3,378 2,835 16.1% Head on 150 88 (117) 41.3% Rear end 938 929 1.0% Right angle 236 222 5.9% Left turn 271 252 7.0% Right turn 23 22 4.3% Sideswipe (same direction) 194 168 13.4% Sideswipe (opposite direction) 270 178 34.1% Others 369 256 30.6% Cross centerline crashes (Head on and Opposite direction sideswipe crashes) 420 266 36.7% 16
Comparison to the National Study NCHRP Study 2009 Louisiana Total Crashes 9% 15% Fatal and Injury (FI) Crashes 12% 31% (fatal), 22% (injury) Total Targeted Crashes 30% 37% FI Head On and Opposite Direction Sideswipe 45% 25% 17
Changes in Crashes by Time and Lighting Condition Time of the Day Before After 6am-12pm 1,398 (24.3%) 1,217 (24.6%) 12pm-6pm 1,962 (34.1%) 1,710 (34.6%) 6pm-12am 1,105 (19.2%) 958 (19.4%) 12am-6am 1,292 (22.4%) 1,054 (21.3%) Lighting Condition Before After Daylight Dark Dawn and Dusk 3,280 2,737 2,328 2,004 192 178 18
Changes in Crashes by Single Vehicle, Driver condition, Alcohol and Pedestrian involvement 19
Safety Effectiveness Estimation with EB M w P ( 1 w ) K i i i i i EB estimate of the expected number of after crashes if countermeasures weren t implemented. Where, K i = total before crashes at site i; P= predicted crashes from SPF; w i = 1 1 + P i k ˆ i var( c ˆ i i M ) i c 2 i (1 w i ) M i Predicted after crashes and variance if countermeasure weren t implemented Where, Ratio of after and before SPF prediction, C i = σ y y=y 0i +1 E(k iy ൯ y=y 0i 1 = Q i E(k iy ൯ P i σ y= 1 ˆ ˆ( ˆ) ˆ[1 ˆ L vâr( ˆ 1 L 1 2 ˆ) ] vâr( ˆ) 2 ˆ vâr( ˆ) 2 ˆ Effectiveness of the countermeasure and its standard error Where, L = total observed crash counts during the after period 20
Crash Modification Factor (CMF) by Empirical Bayes Analysis Estimated CMF θ and standard Error 0.83 (0.016) 0.78 0.83 0.88 28% 17% 12% With certainly, CLTS reduces crashes and CMF could vary between 0.78 and 0.88, which means crash reduction between 12% and 28%) 21
Benefit vs. Cost Injury Type Observed Crash Reduction Crash Cost Safety Benefit Benefit Fatal 44 $1,710,561 $75,264,684 Severe 11 $489,446 $5,383,906 Moderate 196 $173,578 $34,021,288 Complaint 349 $58,636 $20,463,964 None 279 $24,982 $6,969,978 Total Benefit $142,103,820 Cost Unit cost Total Cost FHWA - low $500 $932,665 FHWA high $6,000 $11,191,980 Louisiana - low $700 $1,305,731 Louisiana - high (including traffic control devices, mobilization, raised pavement markers, and striping) $7,632 $14,233,774 22
Benefit Cost Ratio B/C FHWA - low 152 FHWA - high 13 Louisiana - low 109 Louisiana - high 9.98 23
CLRS on rural 2-lane highways Significantly reducing cross-over crashes Providing much needed reduction in fatal and injury crashes Being extremely cost effective 24
Center line rumble strips: an extremely efficient and cost effective crash countermeasure Roundabout Forgiving roadside for rural 2- lane highways Flatten small radius curves Urban complete street Raised Pavement markers RCUT Lane Conversion Pavement edgeline Center line rumble strip Shoulder rumble strip Chevron signs on sharp curves 25
Recommendations Considering CLRS for two-lane highways (state or local, rural or urban) where the cross-center line crash rate (total and/or FI) is higher than the state average. 26
More information on FHWA https://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_strips 27
Urgency for doing everything we can for crash Reduction
Questions? Thank you! xsun@louisiana.edu 29