1. The 2010 Evaluation of Low Cost Safety Improvements Pooled Fund Study Technical Advisory Committee Meeting March 2010 Thomas M. Welch, P.E. State Transportation Safety Engineer Office of Traffic and Safety Iowa Department of Transportation 515 239-1267 tom.welch@dot.iowa.gov 1

2. Horizontal Curve Fatal Crashes 37 63 51 25 97 173 140 334 390 187 127 153 164 808 177 49 298 23 DC 72 209 30 183 35 497 64 487 138 35 675 500 155 385 534 318 27 321 66 77 343 59 89 258 35 84 226 208 163 256 166 101 DC=3 2006-2008 Average From: FHWA Roadway Departure Team 2

3. Percent of Fatal Crashes at Horizontal Curve 54 17 42 37 36 22 27 46 35 29 27 41 23 18 13 26 24 DC 29 20 25 29 30 34 39 35 21 16 22 35 32 36 18 35 40 32 17 35 43 40 24 30 26 25 39 21 44 27 21 44 DC=8 2006-2008 Average From: FHWA Roadway Departure Team 3

4. Primary Highway Curve Crashes Statewide average = 1.1 / MVM (avg radius = 2850 ft., avg length = 870 ft.) Top 30 average = 11.7 (7.2*) / MVM (avg radius = 1780 ft., avg length = 807 ft.) Worst (of top 30) = 78 / MVM 5% of crashes occur at top 30 locations (1% of curves) 11% of fatals occur at top 30 locations * Weighted average 4

5. Low Cost Curve Improvements Super elevation: add or correct Pave shoulders: outside & inside Shoulder rumble strips Flatten outside slope Remove objects outside curve Delineate, chevron, RPM’s (raised pavement markers) Advisory speed plate, ball bank advisory Center line rumble stripe Larger/brighter chevrons 5

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7. District Installed Treatments 43 rural curves have been selected that have had improvements in the last three years, statewide. Improvements were mainly new Chevrons and larger/brighter chevrons. Curves will be cataloged by radius, ADT, etc. 75 to 150 control curves will be selected for comparison. 7

8. Evaluation of Treatments to reduce speeds and crashes on high crash horizontal curves (FHWA funded: Dr. Shauna Hallmark @ Iowa State University PI) Road Upstream Intersection Downstream IntersectionCountyCommentsSpeed/Crash Potential Treatments Final TreatmentAADT L-35/221st StDeacon RdEastman RDMills US 275 (has existing Chevrons) 50 mph advisory; speed problem both directions (85th); 10 crashes, 3 NB/2 SBAll Larger Chevrons or LED2410 Loess Hills TrailKermit PLYork RdHarrisonNo Chevrons 35 mph advisory; speeding both directions; 26 crashes; 12 NB/10 SBPvmt Mkg 1880 IA 141L-32Spruce AveMononaHas Chevrons 35 mph advisory; speeding both directions; 8 crashes; 2 NB/2 SBAll Larger Chevrons830 US 52Clay Hill RdSherrill RdDubuque Possibly large Chevrons (lots of these exist) 40 mph advisory; speed problem 85th both directions; 13 crashes; 4 NB/3 SBReflectors Reflectorized Strip2280 DMC 99 H-50/Stony Hollow Rd150th St Des MoinesNo chevrons no advisory; speed problem 85th SB; 14 crashes; 5 NB/1 SBPvmt Mkg 1430 115 Ave/Y-52 Allens Grove Rd230 StScott Chevrons (small) exist 40 mph advisory; speed problem both directions; 10 crashes; 2 NB/7 SBAll but LED Reflectorized Strip1710 Great River Road (X 56)Larriet Rd Clayton Existing chevrons 45 mph advisory; speed problem 85th both directions; 9 crashes; 3 NB/2 SB Reflector or LED Larger Chevrons or LED1130 8

9. Full Post Chevron (adding reflectorized strip to post) --- chevron is already in place, reflector strip is added to post Pavement Markings (Curve Sign or "SLOW") Solar Powered in-pavement RPM Larger Chevrons 9

10. FY 2011 State of Iowa Funded Safety Program 16 Low Cost Curve Improvement Projects –speed advisory plates –bigger/brighter chevrons –paved shoulders/shoulder rumble strips –centerline rumble strips –25-30 curve improvements $70,000 - Improve signing at “Top 30” Curves 10