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Publication Number: FHWA-RD-97-106

Rural Public Transportation Technologies: User Needs and Applications FR1-798

APPENDIX B

ACCIDENT SEVERITY DISTRIBUTIONS BY RAMP SEGMENT TYPE FOR EIGHT SELECTED RAMP TYPES

This appendix presents accident severity distributions (fatal, injury, and property-damage-only accidents) by ramp segment type for the following eight selected ramp types in tables 48 through 55, respectively:

  • Rural diamond off-ramps.
  • Rural diamond on-ramps.
  • Urban diamond off-ramps.
  • Urban parclo loop off-ramps.
  • Urban free-flow loop off-ramps.
  • Urban outer connection off-ramps.
  • Urban direct and semi-direct connection ramps.
  • Urban C/D roads.

Table 48. Accident Severity Distribution by Ramp Segment Type for Rural Diamond Off-Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
20.4
0.3
70.6
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-
 
-
 
-
0
0
2
-
-
-
-
-
-
-
1
 
0
 
0
0.0
0.0
0.6
-
-
-
-
-
-
-
0.3
 
0.0
 
0.0
6
1
64
-
-
-
-
-
-
-
60
 
0
 
0
1.8
0.3
18.9
-
-
-
-
-
-
-
17.7
 
0.0
 
0.0
15
0
96
-
-
-
-
-
-
-
94
 
0
 
0
4.4
0.0
28.3
-
-
-
-
-
-
-
27.7
 
0.0
 
0.0
21
1
162
-
-
-
-
-
-
-
155
 
0
 
0
6.2
0.3
47.8
-
-
-
-
-
-
-
45.7
 
0.0
 
0.0
Total 91.3 3 0.9 131 38.6 205 60.5 339 100.0

Conversion: 1 mi = 1.61 km

Table 49. Accident Severity Distribution by Ramp Segment Type for Rural Diamond On-Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
0.0
0.0
36.6
47.8
0.4
0.0
0.0
0.0
0.0
0.0
-
 
-
 
-
-
-
0
1
0
-
-
-
-
-
0
 
0
 
0
-
-
0.0
0.7
0.0
-
-
-
-
-
0.0
 
0.0
 
0.0
-
-
2
24
0
-
-
-
-
-
29
 
0
 
0
-
-
1.4
16.8
0.0
-
-
-
-
-
20.3
 
0.0
 
0.0
-
-
8
44
0
-
-
-
-
-
35
 
0
 
0
-
-
5.6
30.8
0.0
-
-
-
-
-
24.5
 
0.0
 
0.0
-
-
10
69
0
-
-
-
-
-
64
 
0
 
0
-
-
7.0
48.3
0.0
-
-
-
-
-
44.8
 
0.0
 
0.0
Total 84.8 1 0.7 55 38.5 87 60.8 143 100.0

Conversion: 1 mi = 1.61 km

Table 50. Accident Severity Distribution by Ramp Segment Type for Urban Diamond Off-Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
13.7
1.2
32.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-
 
-
 
-
0
0
4
-
-
-
0
-
-
-
0
 
0
 
0
0.0
0.0
0.2
-
-
-
0.0
-
-
-
0.0
 
0.0
 
0.0
64
20
372
-
-
-
0
-
-
-
334
 
3
 
0
3.7
1.2
21.6
-
-
-
0.0
-
-
-
19.4
 
0.2
 
0.0
66
23
447
-
-
-
2
-
-
-
383
 
1
 
0
3.8
1.3
26.0
-
-
-
0.1
-
-
-
22.3
 
0.1
 
0.0
130
43
823
-
-
-
2
-
-
-
717
 
4
 
0
7.6
2.5
47.9
-
-
-
0.1
-
-
-
41.7
 
0.2
 
0.0
Total 47.6 4 0.2 793 46.1 922 53.6 1,719 100.0

Conversion: 1 mi = 1.61 km

Table 51. Accident Severity Distribution by Ramp Segment Type for Urban Parclo Loop Off-Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
0.4
0.0
0.8
0.0
0.0
0.1
0.0
0.0
0.0
0.6
-
 
-
 
-
0
-
0
-
-
-
0
-
-
0
0
 
0
 
0
0.0
-
0.0
-
-
-
0.0
-
-
0.0
0.0
 
0.0
 
0.0
64
4
-
18
-
-
0
-
-
5
29
 
0
 
0
3.7
16.5
21.6
-
-
-
0.0
-
-
4.6
26.6
 
0.0
 
0.0
3
-3
14
-
-
-
2
-
-
6
30
 
0
 
0
2.8
-
12.8
-
-
-
0.1
-
-
5.5
27.5
 
0.0
 
0.0
7
-
32
-
-
-
2
-
-
11
59
 
0
 
0
6.4
-
29.4
-
-
-
0.1
-
-
10.1
54.1
 
0.0
 
0.0
Total 1.9 0 0.0 56 51.4 53 48.6 109 100.0

Conversion: 1 mi = 1.61 km

Table 52. Accident Severity Distribution by Ramp Segment Type for Urban Free-Flow Loop Off-Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
0.9
0.1
6.8
0.8
0.0
0.2
0.0
0.0
0.0
0.2
-
 
-
 
-
0
0
1
0
-
0
0
-
-
0
0
 
0
 
0
0.0
0.0
0.4
0.0
-
0.0
0.0
-
-
0.0
0.0
 
0.0
 
0.0
8
0
53
9
-
3
0
-
-
5
0
 
59
 
0
2.8
0.0
18.7
3.2
-
1.1
0.0
-
-
1.8
0.0
 
20.8
 
0.0
8
0
53
9
-
3
0
-
-
5
0
 
59
 
0
2.8
0.0
24.6
3.2
-
2.8
0.4
-
-
2.8
0.0
 
14.8
 
0.0
16
0
124
18
-
11
1
-
-
13
0
 
101
 
0
5.6
0.0
43.7
6.3
-
3.9
0.4
-
-
4.6
0.0
 
35.6
 
0.0
Total 9.0 1 0.4 137 48.2 146 51.4 284 100.0

Conversion: 1 mi = 1.61 km

Table 53. Accident Severity Distribution by Ramp Segment Type for Urban Outer Connection Off-Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
3.0
0.1
9.9
1.1
0.1
0.0
0.0
0.0
0.0
1.8
-
 
-
 
-
0
0
1
0
0
-
0
-
-
0
0
 
0
 
0
0.0
0.0
0.1
0.0
0.0
-
0.0
-
-
0.0
0.0
 
0.0
 
0.0
11
0
148
4
2
-
5
-
-
23
61
 
77
 
0
1.6
0.0
21.2
0.6
0.3
-
0.7
-
-
3.3
8.8
 
11.0
 
0.0
13
0
185
3
4
-
5
-
-
18
70
 
67
 
0
1.9
0.0
26.5
0.4
0.6
-
0.7
-
-
2.6
10.0
 
9.6
 
0.0
24
0
334
7
6
-
10
-
-
18
70
 
67
 
0
3.4
0.0
47.9
1.0
0.9
-
1.4
-
-
5.9
18.8
 
20.7
 
0.0
Total 16.0 1 0.1 331 47.5 365 52.4 697 100.0

Conversion: 1 mi = 1.61 km

Table 54. Accident Severity Distribution by Ramp Segment Type for Urban Direct and Semi-Direct Connection Ramps (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
3.5
1.4
16.5
7.6
2.4
0.2
1.3
1.9
0.0
0.0
-
 
-
 
-
0
0
0
0
0
0
1
0
-
-
0
 
0
 
0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.0
-
-
0.0
 
0.0
 
0.0
11
3
138
43
6
0
19
20
-
-
2
 
16
 
0
2.0
0.5
25.2
7.9
1.1
0.0
3.5
3.7
-
-
0.4
 
2.9
 
0.0
18
6
167
28
15
2
21
13
-
-
4
 
14
 
0
3.3
1.1
30.5
5.1
2.7
0.4
3.8
2.4
-
-
0.7
 
2.6
 
0.0
29
9
305
71
21
2
41
33
-
-
6
 
30
 
0
5.3
1.6
55.8
13.0
3.8
0.4
7.5
6.0
-
-
1.1
 
5.5
 
0.0
Total 34.8 1 0.2 258 47.2 288 52.7 547 100.0

Conversion: 1 mi = 1.61 km

Table 55. Accident Severity Distribution by Ramp Segment Type for Urban C/D Roads (1993 Through 1995)

Ramp segment type Total
length
(mi)
Number and percentage of accidents by severity level
Fatal Injury Property damage
only
Total
Frequency (%) Frequency (%) Frequency (%) Frequency (%)
Normal deceleration lane
Deceleration lane with mainline lane drop
Ramp proper
Normal acceleration lane
Acceleration lane with mainline lane addition
Mainline weaving area
Diverge area on ramp
Merge area on ramp
Weaving area on ramp
Two-way roadway on ramp
Cross-road ramp terminal
  (stop condition)
Cross-road ramp terminal
  (free-flow)
Frontage road connection
3.4
1.1
10.9
7.9
1.7
0.0
3.0
2.0
3.3
0.0
-
 
-
 
-
0
0
3
0
0
-
0
0
0
-
0
 
0
 
0
0.0
0.0
0.3
0.0
0.0
-
0.0
0.0
0.0
-
0.0
 
0.0
 
0.0
5
2
280
11
2
-
80
0
55
-
0
 
0
 
0
0.6
0.2
31.3
1.2
0.2
-
8.9
0.0
6.1
-
0.0
 
0.0
 
0.0
9
4
275
19
7
-
67
0
76
-
0
 
0
 
0
1.0
0.4
30.7
2.1
0.8
-
7.5
0.0
8.5
-
0.0
 
0.0
 
0.0
14
6
558
30
9
-
147
0
131
-
0
 
0
 
0
1.6
0.7
62.3
3.4
1.0
-
16.4
0.0
14.6
-
0.0
 
0.0
 
0.0
Total 33.3 3 0.3 435 48.6 457 51.1 895 100.0

Conversion: 1 mi = 1.61 km

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