- Email: [email protected]
Problem identification, implementation and evaluation of a pedestrian safety program
BiPrer
Acrid Anal . Vol Pnnted m Great Br,tam
14. No 4. pp 315-322. 1981
ooO1~575/82/040315~l7W3 @-J/O 0 1982 Perpamon Press Ltd
PROBLEM IDENTIFICATION, IMPLEMENTATION AND EVALUATION OF A PEDESTRIAN SAFETY PROGRAM JESSIEC. FORTENBERRYand DAVID B. BROWN Department of Industrial and Systems Engineering, University of Alabama, Huntsville AL 35807.U.S.A. (Receired
11September 1980;in
reuised form
4 _lanumy
1982)
Abstract-Through a detailed analysis of accident records of the previous three years, it was observed that young children (6-7 yr of age) were overrepresented in pedestrian accidents in Alabama. In the Fall of 1978, the Alabama Office of Highway and Traffic Safety in conjunction with the state education department, initiated pedestrian safety programs in the four cities of Birmingham, Montgomery, Mobile, and Huntsville. Analysis of the monthly number of pedestrian accidents in these four cities indicated that a statistically significant reduction in pedestrian accidents for the 6-7 yr age group occurred following implementation of the education safety program. Further, it was estimated that approximately 40 accidents were prevented during the evaluation period as a result of the program’s effectiveness. INTRODUCTION
Roadway accidents involving child pedestrians have been a problem of concern throughout the automotive age. With the increasing population and increasing number of automobiles, the problem has become such that the occurrence of roadway accidents is one of the leading causes of childhood deaths. A good deal of work has been done in analyzing the problem; however, there remains much to be done, especially in the area of countermeasure identification and evaluation. This paper presents an analysis of the pedestrian problem in Alabama, describes the educational safety program which was implemented, and evaluates the program vs the basic objective of preventing child pedestrian accidents. Most of the research literature on pedestrian accidents has identified age as being a critical factor in these accidents. The years from 5 to 9 appear to be the age of greatest vulnerability. [Routledge, et al. 19741found that pedestrian accidents show a marked peak for children aged 5-7 yr with boys twice as involved as girls at these ages. Another study [Knoblauch, 19771 analyzed data from 6000 accidents from 7 states for a 3-yr period. It found that 21% of the pedestrian accidents were attributed to the 5-9 yr age group and 42% to the age group of 14 and younger. Salvatore [1974] tested children’s ability to perceive and classify car speed. He found that considerable differences exist in the 5-14 yr age children’s ability to correctly classify car speed as slow, medium or fast. The older the child, the better the judgement. Baker [1977] found that in Baltimore 72% of fatally injured pedestrians were either younger than 10 yr of age, older than 64, or had blood alcohol concentration of 0.10% or higher. This age factor appears to be almost universal in pedestrian accident data and it was prevalent in the Alabama data. PROBLEM
IDENTIFICATION
As part of the development of its Highway Safety Plan (HSP), Alabama performes an in-depth problem identification with respect to traffic accidents each year. This involves the statistical analysis of accident and demographic data to determine the who, what, where, when and why of traffic accidents within the state. For example, of the 128,025 reported traffic accidents in Alabama during 1979, pedestrian accidents were involved in 1262 (about 1%). However, 103 of the pedestrian accidents resulted in fatalities (over ten times the fatality rate of other accidents). Thus, while relatively few in number, pedestrian accidents are a major problem, accounting for over 11% of fatalities. Using the RAPID System [Brown, 19801 developed in Alabama, a special subset of pedestrian accidents was established for detailed analysis. Results of general statewide interest were generated including the following: (1) The most prevalent (33.8%) pedestrian action prior to an accident was crossing the street at a place other than an intersection, 315
J. C. FORTENBERRY and D. B. BROWN
316
(2) About twice as many pedestrian accidents (6.1%) involved those walking with traffic as opposed to those walking against traffic (3.8%), (3) There were three times more males than famales involved in pedestrian accidents, (4) The 6-7 age group had twice as many pedestrian accidents as would be expected from their proportion in the population, (5) The week day after school hours, and especially Fridays after school were highly overrepresented, and (6) Urban areas were highly overrepresented with the four largest cities in Alabama having just slightly under 50% of the pedestrian accidents. Based upon the statewide problem identification discussed above, the decision was made to design a pedestrian program aimed at the 6-7 age group in the cities of Birmingham, Huntsville, Mobile and Montgomery. Further problem identification efforts were then concentrated upon a repetition of the pedestrian analysis but now on the local levels to determine if there were any unique characteristics of pedestrian accidents in these cities that could be integrated into the programs. For example, in Birmingham it was found that the 7-9 a.m. hr were very highly overrepresented (by a factor of 2.3). This was a higher overrepresentation than the after school hours, a phenomenon not usually observed. By integrating problem identification results such as these into the programs, the countermeasures were designed to fit the local areas. As a final step in the budget allocation process a range of costs and benefits was estimated corresponding to the level of effort to be made in the four-cities child pedestrian program. Similarly, all other impact programs competing for funds were assigned costs and benefits. These furnished the input to a dynamic programming optimization routine, DPM [Brosn, 19781.The output was a specification of those countermeasures (and the budgetary levels of each) which were estimated to return the maximum total benefit. Evaluations, such as that discussed below, furnish improved input to the DPM process such that over time the results of the budget allocation process approach the true optimal situation returning the maximum accident reduction benefits. PEDESTRIAN
SAFETY PROGRAMS
Programs were implemented in the first and second grades of the four cities thus aiming for the 6-7 yr age group. Table 1 presents a summary of the number of students involved in the programs. The programs were strictly educational in nature and their objectives were: (1) To help students learn basic pedestrian rules for safe walking, (2) To help students learn correct rules for crossing intersections, and (3) To help students develop an understanding of basic traffic signs and signals. The basic rules stressed in the programs were: (1) Always cross the street at a safe location, (2) Always walk a safe distance from the street to avoid close contact with vehicles, (3) Obey all traffic signs and signals while walking, (4) Do not ride a bicycle in or near the street, (5) Play as far away from the street as possible, (6) Always take the shortest route from one place to another if that route is safe, (7) Look in all directions before crossing at intersections, and (8) Give the right-of-way to all emergency vehicles.
Table 1. Number of students involved in the pedestrian safety program at the four locations Location
number
of Students
Bxrmingham
7,UlO
Huntsrille
1,840
Uobile
u,740
nontgonery
u,ooo
Problem identification, implementation and evaluation of a pedestrian safety program
317
Learning activities of the program included: (1) Taking the students to a street comer and demonstrating the proper way to cross the street; (2) Discussing with the students the reason that it is safer to cross the street at the comer than in the middle of the block, and talling them how the signs and signals help them; (3) Having the students draw two pictures, the first being of a child walking too close to the street, the second being of a child walking a safe distance from the street; (4) Displaying the major traffic signs and signals, discussing each sign and signal and having the students draw the signs and signals on a sheet of paper, and (5) Discussing and demonstrating the meaning of right-of-way. EVALUATION
Data The monthly number of pedestrian accidents were collected for a 4yr period of time, the months corresponding roughly to the school year. This 4 yr period consisted of 2 yr prior to and 2 yr following initiation of the safety programs. Both the monthly number of accidents for the 6-7 yr age group and the monthly number of accidents for all age groups were collected. Table 2 presents the data for the 6-7 yr age group and Table 3 presents data for all age groups. The data in both Tables are for the four-city geographical area under consideration. Statistical
analysis
The objective in this evaluation was to measure any change in the accident frequency for the 6-7 yr age group. In this study, as in many safety evaluations, it was not possible to follow all the procedures which classical experimental design dictates; therefore, it was necessary to resort to quasi-experimental design techniques [Campbell, 19661.The design philosophy was to measure performance parameters in such a manner as to eliminate alternative explanations, other than program effects, for any change observed. To accomplish this a statistic was chosen which would be sensitive to change in number of accidents from the 6-7 yr age group but which would not be sensitive to overall changes in the accident data. The statistic selected was the ratio of the number of accidents in the 6-7 yr age group to the total number of accidents for all other age groups. The number of accidents for all other age groups constituted a control; and Table 2. Monthly number of pedestrian accidents for the &7 yr age group
l!mlttl
‘X-‘77
'77-'78
1
'78-'79
'79-'80
I
I
8
October
7
5
2
lowamber
6
6
I
3
2
December
3
3
I
2
1)
January
2
6
I
6
S
February
7
6
I
0
1
larch
3
6
I
0
3
hpril
S
7
I
3
S
fiar
7
S
I
3
3
June
6
3
I
a
6
July
3
2
I
1
6
August
4
6
I
3
3
Septefibar
5
7
I
S
u
38
uu
I
Total
60
64
I Program Intervention
318
J C FORTENBERR~ and D Table 3 Monthly number of pedestnan ‘lb-‘77
nonttl
B. BROW
accidents for all age groups
‘-IT-‘18
I
‘lib’79
‘79-100
I October
56
56
1
60
57
Noreeber
54
47
f
41
56
December
45
55
I
38
U8
J.%IlWlCY
34
41
I
a3
u2
February
Ul
39
I
33
38
narcti
37
~6
I
u9
uo
April
38
60
1
UO
52
Bar
57
52
I
38
U5
June
35
49
I
51
38
July
UP
52
I
u2
UU
August
44
51
I
44
35
SeQte8beK
50
48
I
46
54
539
596
525
5u9
I Total
I Program
1ntertention
Table 4. Monthly ratios of number of 6-7 yr age group pedestrian accidents to total number for ail other age groups
noath
‘76-‘77
‘77-‘78
‘78-‘79
‘79-“80
I October
. lU3
-095
I
.15u
.036
November
.125
.lU6
I
-079
.037
December
,071
,058
1
-056
.091
January
-063
,171
I
,162
.135
February
-206
. 186
I
,000
-027
narcll
.088
* 150
1
.ooo
-081
API?11
-152
I 132
1
-081
. 106
fl.aY
* 140
-106
I
.ow
-071
JUUe
-296
,Ob5
I
-085
. ld8
July
-073
-340
i
* 02u
-158
August
-100
.ldb
I
.073
.09u
September
-102
.171
I
-122
.080
-078
-0117
1 Yearly
rat&O
. 125
-123
I PrograB Intervention
from observing the figures in Table 3, it appears that this data is fairly stable. Table 4 presents the ratios. These ratios form a time series, the analysis of which is very well documented [Box and Jenkins, 19761.The Box-Jenkins techniques are excellent and sometimes necessary for proper analysis. However, there are some disadvantages associated with the use of those techniques, namely that a relatively large amount of data is needed to properly fit a model. Also, model identification is somewhat subjective. In situations in which there are insufficient
Problem identification, implementation and evaluation of a pedestrian safety program
319
Table 5. Monthly ratios for the “before-after” periods and their differences lontb
After
Difference
.1205
October
-0950
- .0255
-1355
Ilommber
.I3580
- -0775
Before
.06U5
December
- 0735
-0090
-1170
January
.lU85
-0315
-1960
February
-0135
-
.1825
-1190
ttarck
.0405
-
.0785
.lUZO
April
-0935
- .0485
-1230
6ar
.0795
- -0435
-1805
JUPC!
. 1365
- .0440
-0565
July
-0910
-0305
. 1430
August
-0835
- -0595
-1365
September
. 1010
-
-1227
orarall
-0827
- .0100
ratio
-0655
data for the Box-Jenkins model fitting and where no basic statistical principles are violated, a less complicated technique can be used. With this set of data a reduction in both absolute and relative values can be observed (Tables 2 and 4). The purpose of statistical analysis is to measure the probability that the observed reduction occurred by chance. While more than one method may be appropriate for this evaluation, the following nonparametric method was chosen because it was simple to apply and it made very few assumptions. In general, nonparametric techniques require fewer assumptions regarding the parent populations than their parametric counterparts. The ratios of Table 4 were analyzed on a “before-after” basis. Monthly average ratios were computed for the “before” period and the “after” period. These ratios are given in Table 5. Differences for the “after” period when compared with the “before” were also computed and presented. A negative difference indicated that there was a reduction in the ratio following program implementation. Consider the computed differences in Table 5. First of all, there was a reduction in the ratio of the number of pedestrian accidents for the 6-7 age to the total number of pedestrian accidents for all other age groups in nine of the twelve months. The reduction can also be observed in the overall ratios which decreased from 0.1227 for the “before” period to 0.0827 for the “after” period. Another interpretation for the overall ratio reduction is that approximately 12% of the pedestrian accidents prior to program implementation were attributed to the 6-7 yr age group, while only approximately 8% of the accidents were attributed to the 6-7 yr age group following program implementation. The Wilcoxon signed ranks test (Conover, 1971) was used to test the differences of Table 5. The procedure was as follows: Di = yi -xi
where yi is the “after” period ratio, and xi is the “before” period ratio. The test hypotheses were: Ho: Di greater than or equal to 0 Hi: Di less than 0.
Ranks from 1 to 12 were assigned to the Di’s according to the relative size of the absolute AAPVol I4.No4-F
J. C. FORTENBERRY and D. B. B~owti
320
Table 6. Sammy
of Wilcoxon sqped rank test of differences in Table 5
T (Yi Ri)
SDUKCS?
Differences
P
8
< -51
-20 I 0 cl r R
* t . 15
P E D E S ? it -10 I A N R A T -05 I 0
l
0 OEDJPIABJJAS "BEPORE"
ONDJ?IASJJAS "APTER"
Fig. 1. Plot of “Youth Pedestrian Ratio” over time.
difference IDif. A variable Ri was defined for each Di as follows: Ri = 0 if Di was negative Ri = the rank assigned to Di if Di was positive.
The test statistic 7’ was: 7 = I: Ri. Results of the Wilcoxon Signed Ranks test analysis are given in Table 6. The test value was statisticalIy si~ificant (p < 0.01) indicating that a reduction in pedestrian accidents occurred following implementation of the safety programs. A plot of the data contained in Table 5 is presented in Fig. 1. Overall means were included for the “before” and “after” ratio data. CONSfDERATION
OF ALTERNATIVE
EXPLANATlON~
In the evaluation of a field type experiment it is seldom possible to control, and sometimes difficult to monitor, all the factors which could conceivably affect an experiment. In these situations efforts must be made to identify and check as closely as practical factors which could provide an alternate explanation to any effect found in the data. It must then be recognized that alternate explanations may exist and that the conclusions may not be as strong as if they have come from a fully controlled laboratory experiment. However, if only the results of fully controlled laboratory experiments were considered, then most evaluation efforts in safety would be useless.
Problem identification, implementation and evaluation of a pedestrian safety program
321
Clearly a statistically significant reduction occurred in the number of pedestrian accidents for the 6-7 yr age group following program implementation. However, before it can be confirmed that the safety program produced the observed reduction, a careful examination must be made of other factors which may have influenced the number of pedestrian accidents for this particular age group. Some of these factors are: increased traffic enforcement in school zones, decreased traffic density, increased busing, a reduction in the number of 6-7 yr age children, more parks and play areas for children, and modification in street crosswalks and signs for pedestrians around school zones and residential areas. Efforts were made to assertain if any major projects involving these factors had taken place within the treatment time period. While some minor modifications were implemented, as would be expected for continuous improvements, no significant efforts were found toward modifying the pedestrian environment. Also, most environmental factors which might reduce the number of pedestrian accidents for the 6-7 yr age group would probably reduce the number of pedestrian accidents for other age groups. A comparison was made of the number of pedestrian accidents before and after for the 6-7 yr age group with the number of pedestrian accidents for the same time periods for the age groups immediately below and above the 6-7 yr age group. A possible spillover effect may be present in such a comparison due to interactions of children and also since the oldest children in the program during the first year became members of the 8-9 yr age group during the second year. Table 7 presents these accident totals. This comparison shows a large decrease of better than 33% for the 6-7 yr age group for the 2yr following program implementation when compared with a 2 yr period immediately prior to implementation. For the l-5 and 8-9 yr age groups only very small changes were observed. This comparison shows that the decreases for the 6-7 yr age group was unique to that particular age group. It is somewhat regrettable that a larger decrease was not observed for the 8-9 yr age group because one would hope that any learing on the part of the children would carry over with them as they get older. Another comparison was made of the number of pedestrian accidents for the 6-7 yr age group in the 4 cities and the number of pedestrian accidents for the 6-7 yr age group in the rest of the state. Table 8 presents those totals. This comparison indicates that the reduction in accidents for the 6-7 yr age group is unique to the 4 cities involved in the program. While other possible alternate explanations for the observed reduction in the number of pedestrian accidents can not be completely ruled out, comparison with other groups indicate that the reduction is unique to the 4 cities group and to the 6-7 yr age group.
Table 7. The number of pedestrian accidents “before” and “after” for different age groups M==
Group
Total
ZUO Tears
(“before”)
Two Iears [“af term)
Total
Percent Change
l-5
110
113
6-7
12u
82
-33.82
-
0.08
8-9
83
81
-
2.41
Table 8. The total number of pedestnan accidents for the 6-7 yr age group in the four titles and in the rest of the state Total (“before”)
Total (“after”)
Pour Cities
124
82
Statewide
132
133
(except cltles)
four
Percent change
-33.82
l
0.76
322
J. C. F~RTENBERRY and D. B. BROWN ESTIMATED
BENEFITS
After concluding that a reduction had occurred in the relevant accident data set and demonstrating that it was reasonable to assume that the reduction was due to program effectiveness, it was then desirable to estimate benefits. An estimate of the number of accidents prevented was obtained by comparing an expected number of accidents, which would have been expected had a program not been implemented, with the actual number for that period of time. An expected number of accidents was computed by taking the mean ratio (0.1227) for the “before” period and applying it to the “after” period. The ratio was applied to the number of pedestrian accidents for all other age groups. This gave an estimated 122 accidents for the 2 yr evaluation period. Actual number of accidents for that period was 82, giving an estimated savings of 40 accidents for the 4 cities geographical area. SUMMARY
Problem identification indicated that the 6-7 yr age group was overrepresented in pedestrian accidents in Alabama. An educational program was designed based upon local characteristics of pedestrian accidents and implemented in four cities. These programs were aimed at the 6-7 yr age group. A reduction in both the absolute number and relative ratios of pedestrian accidents for this age group was observed following program initiation. Statistical analysis indicates that the reduction was highly significant. Further, it was estimated that approximately 40 pedestrian accidents were prevented during the 2 yr time period following program implementation. REFERENCES Baker S. P., Pedestrian deaths in Rio De Janeiro and Baltimore, Accid. Anal. & Preo. 9. 113-118.1977. Brown D. B., Systems Analysis and Design of Safety. Prentice-Hall, New Jersey, 1976. Brown D. B.. DPM Dynamic Programming Module System Overview and User Guide. Alabama Otlice of Highway and Traffic Safety. Rep. 300-78-002-401-071, April 1978. Brown D. B., RAPID Recrods Analysis for Problem Jdentifcotion and Definition. Alabama Office of Highway and Traffic Safety. Rep. 300-78-002401-095,February 1980. Box G. E. P. and Jenkins G. M.. Time Series Analysis: Forecasting and Control. Holden-Day, San Francisco, CA, 1976. Conover W. J., Practical Nonporametric Statistics. Wiley, New York, 1971. Knoblauch K. L., Accident data base for urban pedestrians, Transpn Res. Rec. No. 629,26-30, 1977. Routledge D. A., Repetto-Wright R., and Howarth C. I., The exposure of young children to accident risk as pedestrians, Ergonomics 17, 1974. Salvatore S., The ability of elementary and secondary school children to sense oncoming car velocity, J. Safety Res. 6, 118-125,1974.
Acrid Anal . Vol Pnnted m Great Br,tam
14. No 4. pp 315-322. 1981
ooO1~575/82/040315~l7W3 @-J/O 0 1982 Perpamon Press Ltd
PROBLEM IDENTIFICATION, IMPLEMENTATION AND EVALUATION OF A PEDESTRIAN SAFETY PROGRAM JESSIEC. FORTENBERRYand DAVID B. BROWN Department of Industrial and Systems Engineering, University of Alabama, Huntsville AL 35807.U.S.A. (Receired
11September 1980;in
reuised form
4 _lanumy
1982)
Abstract-Through a detailed analysis of accident records of the previous three years, it was observed that young children (6-7 yr of age) were overrepresented in pedestrian accidents in Alabama. In the Fall of 1978, the Alabama Office of Highway and Traffic Safety in conjunction with the state education department, initiated pedestrian safety programs in the four cities of Birmingham, Montgomery, Mobile, and Huntsville. Analysis of the monthly number of pedestrian accidents in these four cities indicated that a statistically significant reduction in pedestrian accidents for the 6-7 yr age group occurred following implementation of the education safety program. Further, it was estimated that approximately 40 accidents were prevented during the evaluation period as a result of the program’s effectiveness. INTRODUCTION
Roadway accidents involving child pedestrians have been a problem of concern throughout the automotive age. With the increasing population and increasing number of automobiles, the problem has become such that the occurrence of roadway accidents is one of the leading causes of childhood deaths. A good deal of work has been done in analyzing the problem; however, there remains much to be done, especially in the area of countermeasure identification and evaluation. This paper presents an analysis of the pedestrian problem in Alabama, describes the educational safety program which was implemented, and evaluates the program vs the basic objective of preventing child pedestrian accidents. Most of the research literature on pedestrian accidents has identified age as being a critical factor in these accidents. The years from 5 to 9 appear to be the age of greatest vulnerability. [Routledge, et al. 19741found that pedestrian accidents show a marked peak for children aged 5-7 yr with boys twice as involved as girls at these ages. Another study [Knoblauch, 19771 analyzed data from 6000 accidents from 7 states for a 3-yr period. It found that 21% of the pedestrian accidents were attributed to the 5-9 yr age group and 42% to the age group of 14 and younger. Salvatore [1974] tested children’s ability to perceive and classify car speed. He found that considerable differences exist in the 5-14 yr age children’s ability to correctly classify car speed as slow, medium or fast. The older the child, the better the judgement. Baker [1977] found that in Baltimore 72% of fatally injured pedestrians were either younger than 10 yr of age, older than 64, or had blood alcohol concentration of 0.10% or higher. This age factor appears to be almost universal in pedestrian accident data and it was prevalent in the Alabama data. PROBLEM
IDENTIFICATION
As part of the development of its Highway Safety Plan (HSP), Alabama performes an in-depth problem identification with respect to traffic accidents each year. This involves the statistical analysis of accident and demographic data to determine the who, what, where, when and why of traffic accidents within the state. For example, of the 128,025 reported traffic accidents in Alabama during 1979, pedestrian accidents were involved in 1262 (about 1%). However, 103 of the pedestrian accidents resulted in fatalities (over ten times the fatality rate of other accidents). Thus, while relatively few in number, pedestrian accidents are a major problem, accounting for over 11% of fatalities. Using the RAPID System [Brown, 19801 developed in Alabama, a special subset of pedestrian accidents was established for detailed analysis. Results of general statewide interest were generated including the following: (1) The most prevalent (33.8%) pedestrian action prior to an accident was crossing the street at a place other than an intersection, 315
J. C. FORTENBERRY and D. B. BROWN
316
(2) About twice as many pedestrian accidents (6.1%) involved those walking with traffic as opposed to those walking against traffic (3.8%), (3) There were three times more males than famales involved in pedestrian accidents, (4) The 6-7 age group had twice as many pedestrian accidents as would be expected from their proportion in the population, (5) The week day after school hours, and especially Fridays after school were highly overrepresented, and (6) Urban areas were highly overrepresented with the four largest cities in Alabama having just slightly under 50% of the pedestrian accidents. Based upon the statewide problem identification discussed above, the decision was made to design a pedestrian program aimed at the 6-7 age group in the cities of Birmingham, Huntsville, Mobile and Montgomery. Further problem identification efforts were then concentrated upon a repetition of the pedestrian analysis but now on the local levels to determine if there were any unique characteristics of pedestrian accidents in these cities that could be integrated into the programs. For example, in Birmingham it was found that the 7-9 a.m. hr were very highly overrepresented (by a factor of 2.3). This was a higher overrepresentation than the after school hours, a phenomenon not usually observed. By integrating problem identification results such as these into the programs, the countermeasures were designed to fit the local areas. As a final step in the budget allocation process a range of costs and benefits was estimated corresponding to the level of effort to be made in the four-cities child pedestrian program. Similarly, all other impact programs competing for funds were assigned costs and benefits. These furnished the input to a dynamic programming optimization routine, DPM [Brosn, 19781.The output was a specification of those countermeasures (and the budgetary levels of each) which were estimated to return the maximum total benefit. Evaluations, such as that discussed below, furnish improved input to the DPM process such that over time the results of the budget allocation process approach the true optimal situation returning the maximum accident reduction benefits. PEDESTRIAN
SAFETY PROGRAMS
Programs were implemented in the first and second grades of the four cities thus aiming for the 6-7 yr age group. Table 1 presents a summary of the number of students involved in the programs. The programs were strictly educational in nature and their objectives were: (1) To help students learn basic pedestrian rules for safe walking, (2) To help students learn correct rules for crossing intersections, and (3) To help students develop an understanding of basic traffic signs and signals. The basic rules stressed in the programs were: (1) Always cross the street at a safe location, (2) Always walk a safe distance from the street to avoid close contact with vehicles, (3) Obey all traffic signs and signals while walking, (4) Do not ride a bicycle in or near the street, (5) Play as far away from the street as possible, (6) Always take the shortest route from one place to another if that route is safe, (7) Look in all directions before crossing at intersections, and (8) Give the right-of-way to all emergency vehicles.
Table 1. Number of students involved in the pedestrian safety program at the four locations Location
number
of Students
Bxrmingham
7,UlO
Huntsrille
1,840
Uobile
u,740
nontgonery
u,ooo
Problem identification, implementation and evaluation of a pedestrian safety program
317
Learning activities of the program included: (1) Taking the students to a street comer and demonstrating the proper way to cross the street; (2) Discussing with the students the reason that it is safer to cross the street at the comer than in the middle of the block, and talling them how the signs and signals help them; (3) Having the students draw two pictures, the first being of a child walking too close to the street, the second being of a child walking a safe distance from the street; (4) Displaying the major traffic signs and signals, discussing each sign and signal and having the students draw the signs and signals on a sheet of paper, and (5) Discussing and demonstrating the meaning of right-of-way. EVALUATION
Data The monthly number of pedestrian accidents were collected for a 4yr period of time, the months corresponding roughly to the school year. This 4 yr period consisted of 2 yr prior to and 2 yr following initiation of the safety programs. Both the monthly number of accidents for the 6-7 yr age group and the monthly number of accidents for all age groups were collected. Table 2 presents the data for the 6-7 yr age group and Table 3 presents data for all age groups. The data in both Tables are for the four-city geographical area under consideration. Statistical
analysis
The objective in this evaluation was to measure any change in the accident frequency for the 6-7 yr age group. In this study, as in many safety evaluations, it was not possible to follow all the procedures which classical experimental design dictates; therefore, it was necessary to resort to quasi-experimental design techniques [Campbell, 19661.The design philosophy was to measure performance parameters in such a manner as to eliminate alternative explanations, other than program effects, for any change observed. To accomplish this a statistic was chosen which would be sensitive to change in number of accidents from the 6-7 yr age group but which would not be sensitive to overall changes in the accident data. The statistic selected was the ratio of the number of accidents in the 6-7 yr age group to the total number of accidents for all other age groups. The number of accidents for all other age groups constituted a control; and Table 2. Monthly number of pedestrian accidents for the &7 yr age group
l!mlttl
‘X-‘77
'77-'78
1
'78-'79
'79-'80
I
I
8
October
7
5
2
lowamber
6
6
I
3
2
December
3
3
I
2
1)
January
2
6
I
6
S
February
7
6
I
0
1
larch
3
6
I
0
3
hpril
S
7
I
3
S
fiar
7
S
I
3
3
June
6
3
I
a
6
July
3
2
I
1
6
August
4
6
I
3
3
Septefibar
5
7
I
S
u
38
uu
I
Total
60
64
I Program Intervention
318
J C FORTENBERR~ and D Table 3 Monthly number of pedestnan ‘lb-‘77
nonttl
B. BROW
accidents for all age groups
‘-IT-‘18
I
‘lib’79
‘79-100
I October
56
56
1
60
57
Noreeber
54
47
f
41
56
December
45
55
I
38
U8
J.%IlWlCY
34
41
I
a3
u2
February
Ul
39
I
33
38
narcti
37
~6
I
u9
uo
April
38
60
1
UO
52
Bar
57
52
I
38
U5
June
35
49
I
51
38
July
UP
52
I
u2
UU
August
44
51
I
44
35
SeQte8beK
50
48
I
46
54
539
596
525
5u9
I Total
I Program
1ntertention
Table 4. Monthly ratios of number of 6-7 yr age group pedestrian accidents to total number for ail other age groups
noath
‘76-‘77
‘77-‘78
‘78-‘79
‘79-“80
I October
. lU3
-095
I
.15u
.036
November
.125
.lU6
I
-079
.037
December
,071
,058
1
-056
.091
January
-063
,171
I
,162
.135
February
-206
. 186
I
,000
-027
narcll
.088
* 150
1
.ooo
-081
API?11
-152
I 132
1
-081
. 106
fl.aY
* 140
-106
I
.ow
-071
JUUe
-296
,Ob5
I
-085
. ld8
July
-073
-340
i
* 02u
-158
August
-100
.ldb
I
.073
.09u
September
-102
.171
I
-122
.080
-078
-0117
1 Yearly
rat&O
. 125
-123
I PrograB Intervention
from observing the figures in Table 3, it appears that this data is fairly stable. Table 4 presents the ratios. These ratios form a time series, the analysis of which is very well documented [Box and Jenkins, 19761.The Box-Jenkins techniques are excellent and sometimes necessary for proper analysis. However, there are some disadvantages associated with the use of those techniques, namely that a relatively large amount of data is needed to properly fit a model. Also, model identification is somewhat subjective. In situations in which there are insufficient
Problem identification, implementation and evaluation of a pedestrian safety program
319
Table 5. Monthly ratios for the “before-after” periods and their differences lontb
After
Difference
.1205
October
-0950
- .0255
-1355
Ilommber
.I3580
- -0775
Before
.06U5
December
- 0735
-0090
-1170
January
.lU85
-0315
-1960
February
-0135
-
.1825
-1190
ttarck
.0405
-
.0785
.lUZO
April
-0935
- .0485
-1230
6ar
.0795
- -0435
-1805
JUPC!
. 1365
- .0440
-0565
July
-0910
-0305
. 1430
August
-0835
- -0595
-1365
September
. 1010
-
-1227
orarall
-0827
- .0100
ratio
-0655
data for the Box-Jenkins model fitting and where no basic statistical principles are violated, a less complicated technique can be used. With this set of data a reduction in both absolute and relative values can be observed (Tables 2 and 4). The purpose of statistical analysis is to measure the probability that the observed reduction occurred by chance. While more than one method may be appropriate for this evaluation, the following nonparametric method was chosen because it was simple to apply and it made very few assumptions. In general, nonparametric techniques require fewer assumptions regarding the parent populations than their parametric counterparts. The ratios of Table 4 were analyzed on a “before-after” basis. Monthly average ratios were computed for the “before” period and the “after” period. These ratios are given in Table 5. Differences for the “after” period when compared with the “before” were also computed and presented. A negative difference indicated that there was a reduction in the ratio following program implementation. Consider the computed differences in Table 5. First of all, there was a reduction in the ratio of the number of pedestrian accidents for the 6-7 age to the total number of pedestrian accidents for all other age groups in nine of the twelve months. The reduction can also be observed in the overall ratios which decreased from 0.1227 for the “before” period to 0.0827 for the “after” period. Another interpretation for the overall ratio reduction is that approximately 12% of the pedestrian accidents prior to program implementation were attributed to the 6-7 yr age group, while only approximately 8% of the accidents were attributed to the 6-7 yr age group following program implementation. The Wilcoxon signed ranks test (Conover, 1971) was used to test the differences of Table 5. The procedure was as follows: Di = yi -xi
where yi is the “after” period ratio, and xi is the “before” period ratio. The test hypotheses were: Ho: Di greater than or equal to 0 Hi: Di less than 0.
Ranks from 1 to 12 were assigned to the Di’s according to the relative size of the absolute AAPVol I4.No4-F
J. C. FORTENBERRY and D. B. B~owti
320
Table 6. Sammy
of Wilcoxon sqped rank test of differences in Table 5
T (Yi Ri)
SDUKCS?
Differences
P
8
< -51
-20 I 0 cl r R
* t . 15
P E D E S ? it -10 I A N R A T -05 I 0
l
0 OEDJPIABJJAS "BEPORE"
ONDJ?IASJJAS "APTER"
Fig. 1. Plot of “Youth Pedestrian Ratio” over time.
difference IDif. A variable Ri was defined for each Di as follows: Ri = 0 if Di was negative Ri = the rank assigned to Di if Di was positive.
The test statistic 7’ was: 7 = I: Ri. Results of the Wilcoxon Signed Ranks test analysis are given in Table 6. The test value was statisticalIy si~ificant (p < 0.01) indicating that a reduction in pedestrian accidents occurred following implementation of the safety programs. A plot of the data contained in Table 5 is presented in Fig. 1. Overall means were included for the “before” and “after” ratio data. CONSfDERATION
OF ALTERNATIVE
EXPLANATlON~
In the evaluation of a field type experiment it is seldom possible to control, and sometimes difficult to monitor, all the factors which could conceivably affect an experiment. In these situations efforts must be made to identify and check as closely as practical factors which could provide an alternate explanation to any effect found in the data. It must then be recognized that alternate explanations may exist and that the conclusions may not be as strong as if they have come from a fully controlled laboratory experiment. However, if only the results of fully controlled laboratory experiments were considered, then most evaluation efforts in safety would be useless.
Problem identification, implementation and evaluation of a pedestrian safety program
321
Clearly a statistically significant reduction occurred in the number of pedestrian accidents for the 6-7 yr age group following program implementation. However, before it can be confirmed that the safety program produced the observed reduction, a careful examination must be made of other factors which may have influenced the number of pedestrian accidents for this particular age group. Some of these factors are: increased traffic enforcement in school zones, decreased traffic density, increased busing, a reduction in the number of 6-7 yr age children, more parks and play areas for children, and modification in street crosswalks and signs for pedestrians around school zones and residential areas. Efforts were made to assertain if any major projects involving these factors had taken place within the treatment time period. While some minor modifications were implemented, as would be expected for continuous improvements, no significant efforts were found toward modifying the pedestrian environment. Also, most environmental factors which might reduce the number of pedestrian accidents for the 6-7 yr age group would probably reduce the number of pedestrian accidents for other age groups. A comparison was made of the number of pedestrian accidents before and after for the 6-7 yr age group with the number of pedestrian accidents for the same time periods for the age groups immediately below and above the 6-7 yr age group. A possible spillover effect may be present in such a comparison due to interactions of children and also since the oldest children in the program during the first year became members of the 8-9 yr age group during the second year. Table 7 presents these accident totals. This comparison shows a large decrease of better than 33% for the 6-7 yr age group for the 2yr following program implementation when compared with a 2 yr period immediately prior to implementation. For the l-5 and 8-9 yr age groups only very small changes were observed. This comparison shows that the decreases for the 6-7 yr age group was unique to that particular age group. It is somewhat regrettable that a larger decrease was not observed for the 8-9 yr age group because one would hope that any learing on the part of the children would carry over with them as they get older. Another comparison was made of the number of pedestrian accidents for the 6-7 yr age group in the 4 cities and the number of pedestrian accidents for the 6-7 yr age group in the rest of the state. Table 8 presents those totals. This comparison indicates that the reduction in accidents for the 6-7 yr age group is unique to the 4 cities involved in the program. While other possible alternate explanations for the observed reduction in the number of pedestrian accidents can not be completely ruled out, comparison with other groups indicate that the reduction is unique to the 4 cities group and to the 6-7 yr age group.
Table 7. The number of pedestrian accidents “before” and “after” for different age groups M==
Group
Total
ZUO Tears
(“before”)
Two Iears [“af term)
Total
Percent Change
l-5
110
113
6-7
12u
82
-33.82
-
0.08
8-9
83
81
-
2.41
Table 8. The total number of pedestnan accidents for the 6-7 yr age group in the four titles and in the rest of the state Total (“before”)
Total (“after”)
Pour Cities
124
82
Statewide
132
133
(except cltles)
four
Percent change
-33.82
l
0.76
322
J. C. F~RTENBERRY and D. B. BROWN ESTIMATED
BENEFITS
After concluding that a reduction had occurred in the relevant accident data set and demonstrating that it was reasonable to assume that the reduction was due to program effectiveness, it was then desirable to estimate benefits. An estimate of the number of accidents prevented was obtained by comparing an expected number of accidents, which would have been expected had a program not been implemented, with the actual number for that period of time. An expected number of accidents was computed by taking the mean ratio (0.1227) for the “before” period and applying it to the “after” period. The ratio was applied to the number of pedestrian accidents for all other age groups. This gave an estimated 122 accidents for the 2 yr evaluation period. Actual number of accidents for that period was 82, giving an estimated savings of 40 accidents for the 4 cities geographical area. SUMMARY
Problem identification indicated that the 6-7 yr age group was overrepresented in pedestrian accidents in Alabama. An educational program was designed based upon local characteristics of pedestrian accidents and implemented in four cities. These programs were aimed at the 6-7 yr age group. A reduction in both the absolute number and relative ratios of pedestrian accidents for this age group was observed following program initiation. Statistical analysis indicates that the reduction was highly significant. Further, it was estimated that approximately 40 pedestrian accidents were prevented during the 2 yr time period following program implementation. REFERENCES Baker S. P., Pedestrian deaths in Rio De Janeiro and Baltimore, Accid. Anal. & Preo. 9. 113-118.1977. Brown D. B., Systems Analysis and Design of Safety. Prentice-Hall, New Jersey, 1976. Brown D. B.. DPM Dynamic Programming Module System Overview and User Guide. Alabama Otlice of Highway and Traffic Safety. Rep. 300-78-002-401-071, April 1978. Brown D. B., RAPID Recrods Analysis for Problem Jdentifcotion and Definition. Alabama Office of Highway and Traffic Safety. Rep. 300-78-002401-095,February 1980. Box G. E. P. and Jenkins G. M.. Time Series Analysis: Forecasting and Control. Holden-Day, San Francisco, CA, 1976. Conover W. J., Practical Nonporametric Statistics. Wiley, New York, 1971. Knoblauch K. L., Accident data base for urban pedestrians, Transpn Res. Rec. No. 629,26-30, 1977. Routledge D. A., Repetto-Wright R., and Howarth C. I., The exposure of young children to accident risk as pedestrians, Ergonomics 17, 1974. Salvatore S., The ability of elementary and secondary school children to sense oncoming car velocity, J. Safety Res. 6, 118-125,1974.