Post on 03-Jan-2016
transcript
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 EngineerOffice of Traffic and SafetyIowa Department of Transportation 515 239-1267tom.welch@dot.iowa.gov 1
Horizontal Curve Fatal Crashes
37
63
51
25
97
173 140
334
390
187
127
153
164
808
177
49298
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
226208
163
256
166
101
DC=3
2006-2008 Average
From: FHWA Roadway Departure Team2
Percent of Fatal Crashes at Horizontal Curve
54
17
42
37
36
22 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
3921
44
27
21
44
DC=8
2006-2008 Average
From: FHWA Roadway Departure Team3
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
0
5
10
15
20
25
30
0 2000 4000 6000 8000 10000
Radius (ft)
Cra
sh r
ate
(MV
M)
0
5
10
15
20
25
30
0 500 1000 1500 2000 2500 3000
Length (ft)
Cra
sh r
ate
(MV
M)
4
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 chevrons5
6
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
Evaluation of Treatments to reduce speeds and crashes on high crash horizontal curves
(FHWA funded: Dr. Shauna Hallmark @ Iowa State University PI)
RoadUpstream Intersection
Downstream Intersection County Comments Speed/Crash
Potential Treatments
Final Treatment AADT
L-35/221st St Deacon Rd Eastman RD Mills
US 275 (has existing Chevrons)
50 mph advisory; speed problem both directions (85th); 10 crashes, 3 NB/2 SB All
Larger Chevrons or
LED 2410
Loess Hills Trail Kermit PL York Rd Harrison No Chevrons
35 mph advisory; speeding both directions; 26 crashes; 12 NB/10 SB Pvmt Mkg Pvmt Mkg 1880
IA 141 L-32 Spruce Ave Monona Has Chevrons
35 mph advisory; speeding both directions; 8 crashes; 2 NB/2 SB All
Larger Chevrons 830
US 52 Clay Hill Rd Sherrill Rd Dubuque
Possibly large Chevrons (lots of these exist)
40 mph advisory; speed problem 85th both directions; 13 crashes; 4 NB/3 SB Reflectors
Reflectorized Strip 2280
DMC 99H-50/Stony Hollow Rd 150th St
Des Moines No chevrons
no advisory; speed problem 85th SB; 14 crashes; 5 NB/1 SB Pvmt Mkg Pvmt Mkg 1430
115 Ave/Y-52Allens Grove Rd 230 St Scott
Chevrons (small) exist
40 mph advisory; speed problem both directions; 10 crashes; 2 NB/7 SB All but LED
Reflectorized Strip 1710
Great River Road (X 56) Larriet Rd 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
LED 1130
8
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
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