Factors in the Initiation of Bicycle-Motor Vehicle Collisions Allan F.
Williams,
PhD
\s=b\ In this study, 888 injury-producing bicycle-motor vehicle collisions were ex-
amined. On the basis of the movements of the vehicles involved, the bicyclist or the bicycle or both was probably responsible for the initiation of more than three fourths of the collisions. Bicyclist age was strongly related to probable responsibility for the collision. Through age 12, nine out of ten bicyclists were probably responsible for the collision; above age 12, probable responsibility decreased in proportion to age; and only 34% of the bicyclists aged 25 years or older were probably responsible. Collisions involving bicyclists in various age groups differed considerably in where, when, and how they occurred. The movements of the vehicles primarily involved in the initiation of the collisions were evaluated in terms of countermeasure
(Am
planning.
J Dis Child
130:370-377, 1976)
has been estimated that
It United States
bicycle-
motor vehicle collisions in the account for less than 5% of all injuries to bicyclists,1 but
more than 90% of all bicyclist deaths.2 There has been a substantial increase in fatal bicycle-motor vehicle colli¬ sions in recent years, primarily in the older population. For example, be¬ tween 1970 and 1973, the number of fatally injured bicyclists 15 years and older increased from 280 to 590 (111%), while the number of such bi¬ cyclists under 15 years increased only from 540 to 560 (4%).2·3 Yet, few stud-
Received for publication Dec 11,1974; accepted March 7, 1975. From the Insurance Institute for Highway Safety, Washington, DC. Reprint requests to Research Department, Insurance Institute for Highway Safety, Watergate Six Hundred, Washington, DC 20037 (Dr
Williams).
ies of bicycle-motor vehicle collisions have been undertaken,47 and there is little information available concern¬ ing how such collisone and associated factors differ by age of the bicyclist. In this study, 888 reported bicyclemotor vehicle collisions resulting in injury to the bicyclist, motorist, or passenger of either vehicle were ana¬ lyzed. The main objectives were to study characteristics of the operators involved relative to the probable re¬ sponsibility for the collision of the bicyclist or motorist and/or their ve¬ hicles, based on the precrash move¬ ments of the vehicles, and to examine bicycle-motor vehicle collisions in re¬ lation to bicyclist age. In previous studies, bicyclists have been cited for their "unsafe actions," violation of traffic laws, and the like,4·68 but prob¬ able responsibility for bicycle-motor vehicle collisions has heretofore not been determined on the basis of sys¬ tematic application of objective ve¬ hicle movement criteria associated with crash initiation. METHODS Police reports on 888 of the 895 reported injury-producing bicycle-motor vehicle col¬ lisions occurring in Maryland in the oneyear period, Oct 1, 1971, to Sept 30, 1972, were obtained from the City of Baltimore Police Department and the Maryland State Police. Determinations of probable responsi¬ bility for the collision were based on move¬ ments of the vehicles in the crash, using a modification of criteria developed by Haddon8 in determining probable responsi¬ bility of fatally injured drivers or their ve¬ hicles or both in motor vehicle crashes. The classifications were based exclusively on information from the diagram and narra-
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
tive
description
of the crash
on
the
police
report form. "Responsibility" for the colli¬
sion, as the term is used here, refers to ini¬ tiation of the event, not necessarily culpa¬ bility of the driver or bicyclist. Although hereafter in this article responsibility is referred to in terms of the vehicle oper¬ ator, it should be understood that responsi¬ bility is attributable to the operator or ve¬ hicle or both. Light conditions existing at the time of the collision were classified as daylight, civil twilight, nautical twilight, or dark¬ ness.1011 "Civil twilight" is defined as the period from sunset to the time the center of the sun is —6° below the horizon. The term includes the corresponding period be¬ fore sunrise. "Nautical twilight" is defined as the period from the end of civil twilight to the time the center of the sun is —12° below the horizon, and the corresponding period before sunrise.12 RESULTS and Motorists In the 888 bicycle-motor vehicle col¬ lisions, 99% of the involved bicyclists were injured. Twelve (1%) were killed, 345 (39%) were reported by the police to have received an A-type injury (bleeding wound, distorted member, an injury that required the bicyclist to be carried from the scene); 362 (41%), a B-type injury (other visible injury, such as bruises, abrasions, swelling, limping); and 153 (17%), a Ctype injury (no visible injury but momentary unconsciousness or com¬ plaint of pain). The bicyclist had a passenger in 32 (4%) instances, and 27 (84%) of these passengers were in¬ jured, although none was killed. Only 12 (1%) of the motorists were injured, five suffering an A-type injury, and
Injuries
seven a
to
Bicyclists
B-type injury. emphasized
It should be
that these
-Age 4 9 -Age 10- 14 Age > 15 -All Ages
20 -|
-
/7/\
-
\
15 -
Percent
of
Bicycle-Motor 10Vehicle Collisions
0
I- "~ " Feb
~~ " Mar
"1 " ~" " ~~ " — " — " — " ~T~ ~T~
Oct Nov Fig 1.—Monthly percentages of bicycle-motor vehicle collisions, by age of bicyclist, Oct 1, 1971 to Sept 30, 1972. Jan
injury classifications are usually based exclusively on observations made by the police officer at the scene of the crash, and there is no follow-up that would permit classification of in¬ jury severity on the basis of appropri¬ ate medical criteria. A subsequently developed "Injury Severity Score" is relatively simple to use, and is sub¬ stantially correlated with likelihood of death.13 According to John P. Bull, MD, it also correlates well with
length of hospitalization (written communication, Oct 29, 1974). Bicyclist Characteristics
and Time and Place of Collision
Of the 886 involved
bicyclists whose
less than ages known, 4 years old, 280 (32%) were 4 to 9 years old, 379 (43%) were 10 to 14 years old, 151 (17%) were ages 15 to 19 years, and only 76 (9%) were 20 years of age or older. Eighty-four percent were
none was
males. Most of the collisions
were
(72%)
oc-
Apr
May
Jun
Jul
Aug
curred in the months May through September. There was some variation by day of the week: Monday, 17%;
Tuesday, 13%; Wednesday, 13%; Thursday, 13%; Friday, 16%; Satur¬ day, 16%; and Sunday, 12%. Sixty-five
percent of the collisions took place
from 3 to 9 pm, with 86% occurring during daylight, 3% in civil twilight, 4% in nautical twilight, and 7% in darkness. Seventy-one percent oc¬ curred in residential areas; 8% took place in the same town in which the bicyclist resided; and 67% occurred at intersections. Bicyclist sex was not significantly (P>.05) associated with bicyclist age, police categorization of injury, month, day of week, hour of day, light conditions, or residential or intersection location.
Bicyclist Age Differences.—Figure 1 monthly percentages of bi¬
shows
cycle-motor vehicle collisions occur¬ ring in age groups 4 to 9 years, 10 to 14 years, and 15 years or over. Colli¬ sions involving bicyclists aged 4 to 9
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
Sep
years
~T Dec
peaked in May, and
a
higher
of the collisions involving this age group occurred in May than was the case in other age groups. To a lesser extent, a higher proportion of the collisions involving bicyclists 4 to 9 years old occurred in April and June than was true in other age groups, particularly bicyclists aged 15 years or over. In July and August, however, proportionately fewer collisions oc¬ curred in the 4- to 9-year-old group than in the older age groups. The number of collisions involving bicy¬ clists 10 to 14 years old rose through¬ out the spring and summer months, peaking in August and dropping off sharply in September. Peak months for collisions involving bicyclists 15 years old and over were August and September, and a higher proportion of the collisions involving this age group occurred during these months, particularly September, than in the younger age groups. Figure 2 shows the percentages of
proportion
20
Age 4 -Age 10-Age >
9
-
-
-All
14
15
Ages
15-1 Percent of
Bicycle-Motor Vehicle Collisions
10
5-
\ Mid- 1
23456789 10 11
night
occurred between 4 and 5:59 pm, than in the case of bicyclists 15 years or over. Between 6 and 6:59 pm, propor¬ tionately more collisions occurred in¬ volving bicyclists 4 to 9 years old than in older age groups. Bicycle-motor ve¬ hicle collisions between 9 and 11:59 pm were infrequent, but Fig 2 indicates that a relatively higher proportion of the collisions involving bicyclists 15 years old or older occurred during this time period. Eighty-seven percent of bicyclists aged 4 to 9 years collided with a mo¬ tor vehicle in the same town in which they lived, compared to 82% of bicy¬ clists aged 10-14 years, and 69% of bicyclists 15 years old or older
9 10 11 12
o o
Fig 2.—Hour of day percentages of bicycle-motor vehicle collisions, by age
bicycle-motor vehicle collisions occur¬ ring at various hours of the day, by age of bicyclist. Considerably higher proportions of the collisions involving bicyclists 4 to 9 and 10 to 14 years old
2345678
N1
of
bicyclist, Oct 1,
( 2(2) 25.28, < .001). Eighty-three percent of bicyclists 4 to 9 years old =
crashed in residential areas, 8% in shopping or business areas, and 9% in other areas. Corresponding propor¬ tions for bicyclists aged 10 to 14 years were 71% residential, 20% shopping or business, 10% other locations; and for bicyclists aged 15 years or older, 56% residential, 33% shopping or business, and 11% other locations ( 2(4) 55.42, P< .001). Of bicyclists aged 4 to 9 years, 94% were in collisions in day¬ light, 5% in civil or nautical twilight, and 1% in darkness. Corresponding proportions for bicyclists 10 to 14 years old were 87% daylight, 7% twi¬ light, 6% darkness; and for bicyclists 15 years or over, 73% daylight, 9% twi¬ light and 18% darkness ( 2(6) 60.28, =
=
P .05) associated with police catewas
not
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
1971 to
Sept 30, 1972.
gorization of injury, day of week, and intersection location.
Responsibility
for the Collision
Information on probable responsi¬ bility for the collision is presented in Table 1. As indicated in that table, the bicyclist was judged to be proba¬ bly exclusively responsible in 78% of all the collisions, and the motorist was probably exclusively responsible in 19% of the collisions. In 1% of the collisions, both the bicyclist and motorist were judged to be probably responsible, and in 2% of the cases responsibility was not clear.
Responsibility and Bicyclist Age.—In Fig 3, the percentage of crashes in
which the
bicyclist,
rather than the
motorist, was probably responsible for
the collision is shown in relation to age of the bicyclist. Probable respon¬ sibility was strongly related to bicy-
100 -
95 -
90-
85 80 75
H
Percent of Collisions in Which
65
Bicyclist Probably Respon¬
50-
70
H
60 55 45
sible
-
4035 -
30252015-
1050
Fig 3
Distribution of
30, 1972
4-6
7
8 9
10 11 12 13 14 15 16
bicycle-motor vehicle collisions
in which
17-19
20-24
Table 1.—Probable Responsibility for Bicycle-Motor Vehicle Collisions, Based on Vehicle Movements, Maryland, Oct 1,1971-Sept30, 1972 Collisions
Vehicle Movements Bicycle not in motion; motor vehicle in motion Both bicycle and motor vehicle in motion* Both bicycle and motor vehicle in motionf Both bicycle and motor vehicle in motion:): Bicycle in motion; motor vehicle not in motion Both bicycle and motor vehicle in motion Total
Probable
Responsibility
No. 7 161 644 49 21 888
rii > 19
Motorist Both
Bicyclist Not clear
100
*
Eg, motor vehicle strikes bicycle from rear. t Eg, both vehicles proceed wrong way on one-way street and collide. $ Eg, bicycle comes onto road from lawn or other nonroadway location
and intersects
motor vehicle.
clist age.
the crash.
and it
Vehicle Movements in Crash Initia¬ tion.—In Table 2, the frequency of various vehicle movements associated
Through age 12, the overall percentage of bicyclists probably re¬ sponsible for the collision was 92%, was
not lower than 89% in any
single age category. After age 12, the percentage of probably responsible bicyclists decreased with age. At age 20 and above, less than half of the in¬ volved bicyclists were probably re¬ sponsible. Of the 38 bicyclists aged 25 and over (average age, 33 years), 13 (34%) were probably responsible for
25-1
Bicyclist Age bicyclist was probably responsible, by bicyclist age,
with initiation of the collision is shown separately for crashes in which the bicyclist was probably responsible and for crashes in which the motorist was probably responsible. For crashes in which the bicyclist was probably responsible, vehicle movements are shown in relation to bicyclist age.
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
Oct 1,1971 to
Sept
The most frequent maneuvers of the bicycle in situations in which the
bicyclist were
was
probably responsible
(1) emerging from a minor road¬
as a driveway, alley, park¬ ing lot, or gas station onto a more major road and intersecting another vehicle (27%), and (2) running through a stop or yield sign (22%). The most frequent maneuvers of the
way such
motor vehicle in situations in which the motorist was probably responsible were making a left turn and in the process colliding with an oncoming bicycle (28%), and (2) striking a bi¬ cycle from behind (28%).
Vehicle Movements
by Age
of
Bicy¬
clist.—Table 2 shows that in cases in which the bicyclist was probably re¬ sponsible, there were large age dif¬ ferences in the proportions of bicy¬ clists involved in various types of collisions with motor vehicles. The younger bicyclists in collisions in which the bicyclist was probably re¬ sponsible were far more likely to have emerged from a minor roadway, such as a
driveway,
onto
a more
major
Table 2.—Vehicle Movements by Probable Responsibility in Bicycle-Motor Vehicle Collisions in Relation to Bicyclist Age, Maryland, Oct 1,1971-Sept 30,1972 No.
(%) of Collisions
Bicyclist Probably Responsible Bicyclist, Age,* Vehicle Movement In motion; other vehicle not in motion Struck other vehicle from behind Intersected other vehicle traveling in same direction:): Emerged from driveway, alley, parking lot, gas station, etc Came onto road from lawn or other nonroadway location and intersected other vehicle Ran through stop or yield sign Wrong way on one-way street or in lane desig¬ nated for traffic in opposite direction While making a left turn, collided with oncoming vehicle
Unclassified Total
4-9t 11
(4) 0(0)
19(7)
Motorist
yr
All
10-14
>15
22(7) 0(0) 55(18)
16(13) 1(1) 27 (22)
Bicyclists 49(7) 1 (0) 101 (15)
Probably Responsible 7(4) 47 (28) 19(11)
Total
56(6) 48(6) 120(14)
103(40)
70
(22)
15(12)
188(27)
8(5)
196
40(16) (20)
31 78
(10) (25)
7(6) 20(16)
78(11) 149§(22)
0(0) 19(11)
168
(25) 3(2) 3(2) 123(99)
(15) '(1) 15(2) 693§ (100)
9(5) (28) 12(7) 168(99)
50
(8) 4(2) 7(3) 255(100) 21
(16) 2(1) 5(2) 314(101) 51
31
103
47
(23)
78(9) (20)
(13) (6) 27(3) 861 (100) 112 56
1 bicyclist age: Not computed since >20% of cells have expected frequencies 15 Total
Motorist
Bicyclist Probably Responsible 238 (94) 276 (87) 104(63) 618(84)
Probably Responsible 16(6) 41 (13) 60 (37)
117(16)
Total
254(100) 317(100) 164(100) 735(100)
Bicyclist Probably Responsible 17(100) 38 (78) 19(32) 54 (59)
or
Darknessi
Motorist
Probably Responsible 0(0) 11 (22) 40 (68) 51 (41)
Total
17(100) 49(100) 59(100) 125(100)
2 , responsibility vs light conditions 40.51, P-C001; %2m responsibility vs light conditions (age .10; 2 ) responsi¬ bility vs light conditions (age >15) 15.85, P
Williams,
PhD
\s=b\ In this study, 888 injury-producing bicycle-motor vehicle collisions were ex-
amined. On the basis of the movements of the vehicles involved, the bicyclist or the bicycle or both was probably responsible for the initiation of more than three fourths of the collisions. Bicyclist age was strongly related to probable responsibility for the collision. Through age 12, nine out of ten bicyclists were probably responsible for the collision; above age 12, probable responsibility decreased in proportion to age; and only 34% of the bicyclists aged 25 years or older were probably responsible. Collisions involving bicyclists in various age groups differed considerably in where, when, and how they occurred. The movements of the vehicles primarily involved in the initiation of the collisions were evaluated in terms of countermeasure
(Am
planning.
J Dis Child
130:370-377, 1976)
has been estimated that
It United States
bicycle-
motor vehicle collisions in the account for less than 5% of all injuries to bicyclists,1 but
more than 90% of all bicyclist deaths.2 There has been a substantial increase in fatal bicycle-motor vehicle colli¬ sions in recent years, primarily in the older population. For example, be¬ tween 1970 and 1973, the number of fatally injured bicyclists 15 years and older increased from 280 to 590 (111%), while the number of such bi¬ cyclists under 15 years increased only from 540 to 560 (4%).2·3 Yet, few stud-
Received for publication Dec 11,1974; accepted March 7, 1975. From the Insurance Institute for Highway Safety, Washington, DC. Reprint requests to Research Department, Insurance Institute for Highway Safety, Watergate Six Hundred, Washington, DC 20037 (Dr
Williams).
ies of bicycle-motor vehicle collisions have been undertaken,47 and there is little information available concern¬ ing how such collisone and associated factors differ by age of the bicyclist. In this study, 888 reported bicyclemotor vehicle collisions resulting in injury to the bicyclist, motorist, or passenger of either vehicle were ana¬ lyzed. The main objectives were to study characteristics of the operators involved relative to the probable re¬ sponsibility for the collision of the bicyclist or motorist and/or their ve¬ hicles, based on the precrash move¬ ments of the vehicles, and to examine bicycle-motor vehicle collisions in re¬ lation to bicyclist age. In previous studies, bicyclists have been cited for their "unsafe actions," violation of traffic laws, and the like,4·68 but prob¬ able responsibility for bicycle-motor vehicle collisions has heretofore not been determined on the basis of sys¬ tematic application of objective ve¬ hicle movement criteria associated with crash initiation. METHODS Police reports on 888 of the 895 reported injury-producing bicycle-motor vehicle col¬ lisions occurring in Maryland in the oneyear period, Oct 1, 1971, to Sept 30, 1972, were obtained from the City of Baltimore Police Department and the Maryland State Police. Determinations of probable responsi¬ bility for the collision were based on move¬ ments of the vehicles in the crash, using a modification of criteria developed by Haddon8 in determining probable responsi¬ bility of fatally injured drivers or their ve¬ hicles or both in motor vehicle crashes. The classifications were based exclusively on information from the diagram and narra-
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
tive
description
of the crash
on
the
police
report form. "Responsibility" for the colli¬
sion, as the term is used here, refers to ini¬ tiation of the event, not necessarily culpa¬ bility of the driver or bicyclist. Although hereafter in this article responsibility is referred to in terms of the vehicle oper¬ ator, it should be understood that responsi¬ bility is attributable to the operator or ve¬ hicle or both. Light conditions existing at the time of the collision were classified as daylight, civil twilight, nautical twilight, or dark¬ ness.1011 "Civil twilight" is defined as the period from sunset to the time the center of the sun is —6° below the horizon. The term includes the corresponding period be¬ fore sunrise. "Nautical twilight" is defined as the period from the end of civil twilight to the time the center of the sun is —12° below the horizon, and the corresponding period before sunrise.12 RESULTS and Motorists In the 888 bicycle-motor vehicle col¬ lisions, 99% of the involved bicyclists were injured. Twelve (1%) were killed, 345 (39%) were reported by the police to have received an A-type injury (bleeding wound, distorted member, an injury that required the bicyclist to be carried from the scene); 362 (41%), a B-type injury (other visible injury, such as bruises, abrasions, swelling, limping); and 153 (17%), a Ctype injury (no visible injury but momentary unconsciousness or com¬ plaint of pain). The bicyclist had a passenger in 32 (4%) instances, and 27 (84%) of these passengers were in¬ jured, although none was killed. Only 12 (1%) of the motorists were injured, five suffering an A-type injury, and
Injuries
seven a
to
Bicyclists
B-type injury. emphasized
It should be
that these
-Age 4 9 -Age 10- 14 Age > 15 -All Ages
20 -|
-
/7/\
-
\
15 -
Percent
of
Bicycle-Motor 10Vehicle Collisions
0
I- "~ " Feb
~~ " Mar
"1 " ~" " ~~ " — " — " — " ~T~ ~T~
Oct Nov Fig 1.—Monthly percentages of bicycle-motor vehicle collisions, by age of bicyclist, Oct 1, 1971 to Sept 30, 1972. Jan
injury classifications are usually based exclusively on observations made by the police officer at the scene of the crash, and there is no follow-up that would permit classification of in¬ jury severity on the basis of appropri¬ ate medical criteria. A subsequently developed "Injury Severity Score" is relatively simple to use, and is sub¬ stantially correlated with likelihood of death.13 According to John P. Bull, MD, it also correlates well with
length of hospitalization (written communication, Oct 29, 1974). Bicyclist Characteristics
and Time and Place of Collision
Of the 886 involved
bicyclists whose
less than ages known, 4 years old, 280 (32%) were 4 to 9 years old, 379 (43%) were 10 to 14 years old, 151 (17%) were ages 15 to 19 years, and only 76 (9%) were 20 years of age or older. Eighty-four percent were
none was
males. Most of the collisions
were
(72%)
oc-
Apr
May
Jun
Jul
Aug
curred in the months May through September. There was some variation by day of the week: Monday, 17%;
Tuesday, 13%; Wednesday, 13%; Thursday, 13%; Friday, 16%; Satur¬ day, 16%; and Sunday, 12%. Sixty-five
percent of the collisions took place
from 3 to 9 pm, with 86% occurring during daylight, 3% in civil twilight, 4% in nautical twilight, and 7% in darkness. Seventy-one percent oc¬ curred in residential areas; 8% took place in the same town in which the bicyclist resided; and 67% occurred at intersections. Bicyclist sex was not significantly (P>.05) associated with bicyclist age, police categorization of injury, month, day of week, hour of day, light conditions, or residential or intersection location.
Bicyclist Age Differences.—Figure 1 monthly percentages of bi¬
shows
cycle-motor vehicle collisions occur¬ ring in age groups 4 to 9 years, 10 to 14 years, and 15 years or over. Colli¬ sions involving bicyclists aged 4 to 9
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
Sep
years
~T Dec
peaked in May, and
a
higher
of the collisions involving this age group occurred in May than was the case in other age groups. To a lesser extent, a higher proportion of the collisions involving bicyclists 4 to 9 years old occurred in April and June than was true in other age groups, particularly bicyclists aged 15 years or over. In July and August, however, proportionately fewer collisions oc¬ curred in the 4- to 9-year-old group than in the older age groups. The number of collisions involving bicy¬ clists 10 to 14 years old rose through¬ out the spring and summer months, peaking in August and dropping off sharply in September. Peak months for collisions involving bicyclists 15 years old and over were August and September, and a higher proportion of the collisions involving this age group occurred during these months, particularly September, than in the younger age groups. Figure 2 shows the percentages of
proportion
20
Age 4 -Age 10-Age >
9
-
-
-All
14
15
Ages
15-1 Percent of
Bicycle-Motor Vehicle Collisions
10
5-
\ Mid- 1
23456789 10 11
night
occurred between 4 and 5:59 pm, than in the case of bicyclists 15 years or over. Between 6 and 6:59 pm, propor¬ tionately more collisions occurred in¬ volving bicyclists 4 to 9 years old than in older age groups. Bicycle-motor ve¬ hicle collisions between 9 and 11:59 pm were infrequent, but Fig 2 indicates that a relatively higher proportion of the collisions involving bicyclists 15 years old or older occurred during this time period. Eighty-seven percent of bicyclists aged 4 to 9 years collided with a mo¬ tor vehicle in the same town in which they lived, compared to 82% of bicy¬ clists aged 10-14 years, and 69% of bicyclists 15 years old or older
9 10 11 12
o o
Fig 2.—Hour of day percentages of bicycle-motor vehicle collisions, by age
bicycle-motor vehicle collisions occur¬ ring at various hours of the day, by age of bicyclist. Considerably higher proportions of the collisions involving bicyclists 4 to 9 and 10 to 14 years old
2345678
N1
of
bicyclist, Oct 1,
( 2(2) 25.28, < .001). Eighty-three percent of bicyclists 4 to 9 years old =
crashed in residential areas, 8% in shopping or business areas, and 9% in other areas. Corresponding propor¬ tions for bicyclists aged 10 to 14 years were 71% residential, 20% shopping or business, 10% other locations; and for bicyclists aged 15 years or older, 56% residential, 33% shopping or business, and 11% other locations ( 2(4) 55.42, P< .001). Of bicyclists aged 4 to 9 years, 94% were in collisions in day¬ light, 5% in civil or nautical twilight, and 1% in darkness. Corresponding proportions for bicyclists 10 to 14 years old were 87% daylight, 7% twi¬ light, 6% darkness; and for bicyclists 15 years or over, 73% daylight, 9% twi¬ light and 18% darkness ( 2(6) 60.28, =
=
P .05) associated with police catewas
not
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
1971 to
Sept 30, 1972.
gorization of injury, day of week, and intersection location.
Responsibility
for the Collision
Information on probable responsi¬ bility for the collision is presented in Table 1. As indicated in that table, the bicyclist was judged to be proba¬ bly exclusively responsible in 78% of all the collisions, and the motorist was probably exclusively responsible in 19% of the collisions. In 1% of the collisions, both the bicyclist and motorist were judged to be probably responsible, and in 2% of the cases responsibility was not clear.
Responsibility and Bicyclist Age.—In Fig 3, the percentage of crashes in
which the
bicyclist,
rather than the
motorist, was probably responsible for
the collision is shown in relation to age of the bicyclist. Probable respon¬ sibility was strongly related to bicy-
100 -
95 -
90-
85 80 75
H
Percent of Collisions in Which
65
Bicyclist Probably Respon¬
50-
70
H
60 55 45
sible
-
4035 -
30252015-
1050
Fig 3
Distribution of
30, 1972
4-6
7
8 9
10 11 12 13 14 15 16
bicycle-motor vehicle collisions
in which
17-19
20-24
Table 1.—Probable Responsibility for Bicycle-Motor Vehicle Collisions, Based on Vehicle Movements, Maryland, Oct 1,1971-Sept30, 1972 Collisions
Vehicle Movements Bicycle not in motion; motor vehicle in motion Both bicycle and motor vehicle in motion* Both bicycle and motor vehicle in motionf Both bicycle and motor vehicle in motion:): Bicycle in motion; motor vehicle not in motion Both bicycle and motor vehicle in motion Total
Probable
Responsibility
No. 7 161 644 49 21 888
rii > 19
Motorist Both
Bicyclist Not clear
100
*
Eg, motor vehicle strikes bicycle from rear. t Eg, both vehicles proceed wrong way on one-way street and collide. $ Eg, bicycle comes onto road from lawn or other nonroadway location
and intersects
motor vehicle.
clist age.
the crash.
and it
Vehicle Movements in Crash Initia¬ tion.—In Table 2, the frequency of various vehicle movements associated
Through age 12, the overall percentage of bicyclists probably re¬ sponsible for the collision was 92%, was
not lower than 89% in any
single age category. After age 12, the percentage of probably responsible bicyclists decreased with age. At age 20 and above, less than half of the in¬ volved bicyclists were probably re¬ sponsible. Of the 38 bicyclists aged 25 and over (average age, 33 years), 13 (34%) were probably responsible for
25-1
Bicyclist Age bicyclist was probably responsible, by bicyclist age,
with initiation of the collision is shown separately for crashes in which the bicyclist was probably responsible and for crashes in which the motorist was probably responsible. For crashes in which the bicyclist was probably responsible, vehicle movements are shown in relation to bicyclist age.
Downloaded From: http://archpedi.jamanetwork.com/ by a University of Michigan User on 06/20/2015
Oct 1,1971 to
Sept
The most frequent maneuvers of the bicycle in situations in which the
bicyclist were
was
probably responsible
(1) emerging from a minor road¬
as a driveway, alley, park¬ ing lot, or gas station onto a more major road and intersecting another vehicle (27%), and (2) running through a stop or yield sign (22%). The most frequent maneuvers of the
way such
motor vehicle in situations in which the motorist was probably responsible were making a left turn and in the process colliding with an oncoming bicycle (28%), and (2) striking a bi¬ cycle from behind (28%).
Vehicle Movements
by Age
of
Bicy¬
clist.—Table 2 shows that in cases in which the bicyclist was probably re¬ sponsible, there were large age dif¬ ferences in the proportions of bicy¬ clists involved in various types of collisions with motor vehicles. The younger bicyclists in collisions in which the bicyclist was probably re¬ sponsible were far more likely to have emerged from a minor roadway, such as a
driveway,
onto
a more
major
Table 2.—Vehicle Movements by Probable Responsibility in Bicycle-Motor Vehicle Collisions in Relation to Bicyclist Age, Maryland, Oct 1,1971-Sept 30,1972 No.
(%) of Collisions
Bicyclist Probably Responsible Bicyclist, Age,* Vehicle Movement In motion; other vehicle not in motion Struck other vehicle from behind Intersected other vehicle traveling in same direction:): Emerged from driveway, alley, parking lot, gas station, etc Came onto road from lawn or other nonroadway location and intersected other vehicle Ran through stop or yield sign Wrong way on one-way street or in lane desig¬ nated for traffic in opposite direction While making a left turn, collided with oncoming vehicle
Unclassified Total
4-9t 11
(4) 0(0)
19(7)
Motorist
yr
All
10-14
>15
22(7) 0(0) 55(18)
16(13) 1(1) 27 (22)
Bicyclists 49(7) 1 (0) 101 (15)
Probably Responsible 7(4) 47 (28) 19(11)
Total
56(6) 48(6) 120(14)
103(40)
70
(22)
15(12)
188(27)
8(5)
196
40(16) (20)
31 78
(10) (25)
7(6) 20(16)
78(11) 149§(22)
0(0) 19(11)
168
(25) 3(2) 3(2) 123(99)
(15) '(1) 15(2) 693§ (100)
9(5) (28) 12(7) 168(99)
50
(8) 4(2) 7(3) 255(100) 21
(16) 2(1) 5(2) 314(101) 51
31
103
47
(23)
78(9) (20)
(13) (6) 27(3) 861 (100) 112 56
1 bicyclist age: Not computed since >20% of cells have expected frequencies 15 Total
Motorist
Bicyclist Probably Responsible 238 (94) 276 (87) 104(63) 618(84)
Probably Responsible 16(6) 41 (13) 60 (37)
117(16)
Total
254(100) 317(100) 164(100) 735(100)
Bicyclist Probably Responsible 17(100) 38 (78) 19(32) 54 (59)
or
Darknessi
Motorist
Probably Responsible 0(0) 11 (22) 40 (68) 51 (41)
Total
17(100) 49(100) 59(100) 125(100)
2 , responsibility vs light conditions 40.51, P-C001; %2m responsibility vs light conditions (age .10; 2 ) responsi¬ bility vs light conditions (age >15) 15.85, P
