DriftOff Crashes

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Drift-Off Crashes and the RUMBLE STRIPS that
prevent them
Dave Morena FHWA Michigan Division Sep 20, 2007
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What is a drift-off crash?
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Drift-off crashes are Run-off-road crashes where

• Driver ASLEEP, DROWSY
• Driver DISTRACTED

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Drift-off crashes are NOT

• swerve to avoid another vehicle
• hydroplane
• swerve to avoid debris
• tire blowout
• trailer sway

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What do we know about drift-off crashes?
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2002 study Drift-off crashes Michigan freeways

• 1887 crashes
• 1996 - 2001

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Drift-off crashes are

• Driver ASLEEP, DROWSY
• Driver DISTRACTED

- 82 - 18
(As specified on 1043 reports)
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Severity Quiz
3 times as severe
ASLEEP / DISTRACTED vs. AVOID VEHICLE or OBJECT
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Severity Quiz
5 times as severe
ASLEEP / DISTRACTED vs. HYDROPLANE ??
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Michigan Freeway Crashes - Severity
1996 - 2001
0 .4 KA
On-Road (deer)
6.1 KA
Run-Off-Road
Multiple Vehicle
K fatality A incapacitating injury B
other injury C possible injury O property
damage only
2. 9 KA
34,000 crashes/yr
mainline
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Michigan Freeway Crashes - Severity
1996 - 2001
ice, snow on road 2.9 KA
wet road 3.4 KA
avoid veh, enter, exit, change lanes, passing
6.1 KA
Run-Off-Road
Vehicle defect 5.8 KA
17 KA
34,000 crashes/yr
mainline
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CRASH SEVERITY - KA
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Drift-off crash PROFILE
Michigan freeway
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Vehicles drift off which side of road?
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time of day
Drift off Crashes by Time of Day
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Dark - 55 Light - 45
6
5
Avg 4.2
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Percent of Crashes
3
2
1
0
1
3
5
7
9
11
13
15
17
19
21
23
Time of Day
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Drift off Crashes by Day of Week
25
20
20.3
17.8
Avg 14. 3
15
13.2
13.5
Percent of Accidents
12.2
11.5
11.4
10
5
0
Sun
Mon
Tues
Wed
Thur
Fri
Sat
Day Of Week
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Drift-off Vehicles by Gender of Driver
Males account for 59 of all Michigan
crashes, 71
of fatalities
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Drift-off Vehicles Driver Age
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Drift-off Vehicles Driver Age
All Michigan crashes
Drift off crashes
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Truck Involvement
Trucks accounted for 11 of daily vehicle
miles
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Alcohol Involvement
Driver had been drinking in 21 of all drift-off
crashes
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What can happen to a drift-off vehicle?
???

• recover (no crash)

• parked vehicle
• trees
• signpost, light pole
• guardrail, bridge rail
• hit opposing vehicle
• side slope, ditch

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14
6
20
1
45
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Once a wheel drops off paved shoulder, drivers
have difficulty controlling vehicle
In 1794 crashes
- 32

• over-correct steering
• rollover

- 45
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Crash FREQUENCY
less than one crash / mile / year
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Crash RATE
Drivers less likely to drift off on high-volume
road
No rumble strips
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From crash data, problem areas

• early morning hours
• low volume roads
• curves
• young driver

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A MACHINE TO CUT RUMBLE STRIPS
750 / mile / shoulder
7 x 16 x ½
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Effect of milled shoulder rumble strips on
freeway DRIFT-OFF crashes
100
40 reduction total crashes
60
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7.2
58 reduction KA
17 KA
12 KA
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Concrete intermittent Rumbles
Should we install milled rumbles over concrete
intermittent?
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Concrete intermittent Rumbles
Yes provide continuous alert
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Rolled-in Rumble Strips
Should we install milled rumbles over rolled?
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Yes Milled rumbles provide vibration
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ROLLED
TIRE DROP
MILLED
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How do these rumbles affect large-tired vehicles?
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Bus/truck rumble demonstrationFeb 17, 2000 -
Lansing, MI
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Answer
MILLED - vibrates steering wheel, some
noise ROLLED - slight noise, drowned out by
cab noise CONCRETE INTERMITTENT - drivers
unaware
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Questions Comments

• Dave Morena
• FHWA Michigan Division
• 517-702-1836
• David.Morena_at_fhwa.dot.gov