Jaeyoung Lee Dr. Mohamed Abdel-Aty Ph.D Dr. Mohamed Ahmed …

Jaeyoung Lee, Ph.D Candidate

Dr. Mohamed Abdel-Aty, Ph.D

Dr. Mohamed Ahmed, Ph.D

Traffic Safety under Reduced Visibility 2

• Florida is among the top state in the US regarding traffic safety

problems resulting from adverse visibility conditions due to

fog/smoke and heavy rain.

Crashes due to Reduced Visibility

2,664

2,052

2,021

Texas

Fl

California

Number of Fatal Crashes due to Fog/Smoke/Rain in 2001-2010


Pile-up Crash on I-75 in 2012

• Recently, 10 people were killed and another 18 were injured

from fog/smoke related pile-up crash on I-75 near Gainesville

(Jan 29, 2012).


Severity of Visibility related Crashes

• Generally, Crashes due to reduced visibility from fog/smoke

are more severe compared to non-fog related crashes.

0%

10%

20%

30%

40%

50%

60%

PDOPossible Injury

Non-incapacitatingInjury

IncapacitatingInjury

Fatality

51%

24%

17%

7%

1%

42%

20%23%

10%

5%

Clear Vision

Fog or Smoke


Temporal Distributions (1/4)

• Hourly distribution of fog crashes shows that early hours of

dawn & subsequent hours where fog is prominent (5-8 AM).

4% 4%6% 6%

5%

12%

23%

21%

6%

1%0% 0% 0% 0% 0% 0% 0% 0% 1% 1% 1%

2% 2% 2%

0%

5%

10%

15%

20%

25%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Cra

sh P

erc

ent

age

Military Hours (24h)

Fog

CVState Roads (2005-2010) in Florida



• Hourly distribution of smoke crashes does not show any

obtrusive patterns, which implies smoke crashes do not occur

at specific time period.

2% 3% 3%2% 2% 2%

3%

10%

5%6%

5% 5%4%

7% 6%5%

4% 5% 5%

3%2%

5% 5%

3%

0%

5%

10%

15%

20%

25%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Cra

sh P

erc

enta

ge

Military Hours (24h)

Smoke




• Monthly distribution of fog crashes indicated nearly 60% of

fog crashes occurs during the winter period, from Dec to Feb.

24%

14%

9%

5% 5%

2% 2% 2%2%

7%9%

20%

0%

5%

10%

15%

20%

25%

30%

1 2 3 4 5 6 7 8 9 10 11 12

Cra

sh P

erc

enta

ge

Month

Fog




• Monthly distribution of smoke crashes showed it most

frequently occurs in May which is the dry period.

8% 8%6%

10%

25%

7%8%

4%

6%7%

5%

8%

0%

5%

10%

15%

20%

25%

30%

1 2 3 4 5 6 7 8 9 10 11 12

Cra

sh P

erc

enta

ge

Month

Smoke



Spatial Distributions (1/3)

• Kernel density estimation was used to identify fog/smoke

crash hotspots.

Cluster County Cluster County

1 Pinellas, Hillsborough & Pasco 7 Miami-Dade & Broward

2 Polk & Osceola 8 Lee & Charlotte

3 Duval 9 Glades & Hendry

4 Leon 10 Bay

5 Alachua 11 Brevard & Orange

6 Orange


Hotspot Identification in Florida




• 11 hotspots were magnified and divided highways into one

mile segments and thus FS crashes were counted based on the

segments.



• Segment 2 on I-75 were identified as a fog/smoke crash

hotspot using previous crash data (2005-2010), the pile-up

crash occurred due to fog & smoke involving large trucks at

the very same location.

• Thus, this crash could be avoided

if appropriate treatments were

conducted, proactively.


Contributing Factors (1/3)

• Fog crashes are more frequent at the roadway with poor

lighting condition, divided median, and at segments (not

intersections) in the rural area.

0%

10%

20%

30%

40%

50%

60%

70%

DaylightDusk

DawnDark (street

lighting) Dark (nostreet

lighting)

24%

2%

18% 20%

36%

68%

2%1%

21%

7%

Fog

CV

Fog crashes by lighting conditions



0%

10%

20%

30%

40%

50%

60%

State HighwayLocal Roadway

54%

46%

59%

41%

0%

20%

40%

60%

80%

100%

UrbanRural

48% 52%

85%

15%

Fog

CV

0%

10%

20%

30%

40%

50%

60%

DividedUndivided

41%

59%55%

45%

0%10%20%30%40%50%60%

SegmentAt

intersection Influencedby

intersection

56%

39%

5%

45% 47%

8%

Fog crashes by roadway types Fog crashes by community types

Fog crashes by median types Fog crashes by locations



• Smoke crashes are more frequent at the roadway with poor

lighting condition, and at segments (not at intersections) in the

rural area.

0%

20%

40%

60%

80%

Daylight Dusk Dawn Dark (streetlighting)

Dark (no streetlighting)

57%

1% 7%15% 20%

68%

2% 1%

21%7%

Smoke

CV

0%

20%

40%

60%

80%

100%

Urban Rural

49% 51%

85%

15%

0%

20%

40%

60%

80%

Segment At intersection Influenced byintersection

70%

25%

5%

45% 47%

8%


Frequent Crash Types in Fog Crashes

• Fog crashes lead to more severe injuries and are associated

with rear-end crashes compared to crashes in clear vision (CV)

conditions.

• Moreover, multivehicle, rear-end, head-on or angle crashes

occurring in foggy conditions have significantly higher

probability to result in severe crashes.

0.00 0.50 1.00 1.50 2.00 2.50

Severe injury

Rear-end

Severe injury × Multiple

Severe injury × Rear-end

Severe injury × Head-on

Severe injury × Angle

1.88

1.40

2.06

2.04

1.63

1.81

Odds ratio of crash types and their interactions in fog to CV crash


Frequent Crash Types in Smoke Crashes

• Smoke crashes lead to more severe injury crashes and are

associated with multiple, rear-end and head-on crashes.

• In addition, multivehicle, rear-end or head-on or angle crashes

occurring in smoky conditions have higher probability to result

in severe crashes.

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Severe injury

Multiple vehicle

Rear-end

Head-on

Severe injury × Multiple vehicle

Severe injury × Rear-end

Severe injury × Head-on

1.21

1.10

1.15

1.03

2.99

1.64

1.07

Odds ratio of crash types and their interactions in smoke to CV crash


Summary (1/3)

• Florida is among the top state in the US regarding traffic

safety problems resulting from adverse visibility conditions

due to fog/smoke and heavy rain.

• Crashes due to reduced visibility from fog/smoke are more

severe compared to non-fog related crashes.

• Fog crashes occur mostly in the morning in Dec to Feb,

whereas smoke related crashes occur most frequently in May.


Summary (2/3)

• Roadway with poor lighting condition, undivided segments

(not at intersection) in the rural area has the increased

probability of fog/smoke crash occurrence.

• Through the macroscopic analysis, we can understand the big

picture of fog/smoke crashes, and more specific segments

with frequent fog/smoke crashes can be identified through

micro-level analysis.


Summary (3/3)

• Both fog and smoke crashes lead to more severe injuries

compared to crashes in CV conditions.

• Furthermore, multivehicle, rear-end, head-on or angle crashes

occurring in foggy conditions have significantly higher

probability to result in severe crashes.

Jaeyoung Lee, Ph.D Candidate

Dr. Mohamed Abdel-Aty, Ph.D

Dr. Mohamed Ahmed, Ph.D

Documents

Jaeyoung Lee Dr. Mohamed Abdel-Aty Ph.D Dr. Mohamed Ahmed …