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Evaluation of Critical Highway Safety Needs of Special Population Groups THIS FEATURE EXPLAINS

THE UNITED STATES HAS MADE dramatic progress in the past several THE IDENTIFICATION OF decades in highway safety. But still, millions of people get injured and tens of THE MOST CRITICAL thousands of people get killed each year as a result of highway crashes. The HIGHWAY-SAFETY ISSUES amount of economic losses to the country due to these crashes is estimated to be OF SIX SPECIAL more than $150 billion each year, indicating that there is much work to be POPULATION GROUPS, done in this field.1 One area that offers promise for further progress in relation to WHICH ARE OLDER highway safety in the United States is related to special population groups. DRIVERS, YOUNG Highway-safety needs of special population groups are different from each other DRIVERS, INTERNATIONAL and also from the average population. Certain population groups may have TOURISTS, SCHOOL-AGE higher potential to be involved in highway crashes. Among the several subsets, CHILDREN, NEW six special population groups that can be expected to have some serious highwayIMMIGRANTS AND safety concerns were selected for the purpose of this study. Selected groups PERSONS WITH include older drivers, young drivers, international tourists, school-age chilDISABILITIES. dren, new immigrants and persons with disabilities. Ranking was developed among these special population groups and then critical issues under each group were ranked by applying weights for different criteria considered important in the decision-making process. The rapidly increasing elderly population of the United States and Florida depends more and more on the automobile for most of their mobility needs. Although preserving the mobility of the elderly is of primary concern, traffic-safety statistics BY SUNANDA DISSANAYAKE, JIAN JOHN LU, clearly indicate that XUEHAO CHU AND PATRICIA TURNER older drivers as a group experience an above-average risk of injury and fatality when using the roadways.2 Decreased physical and mental capabilities combined with the frailty of the elderly affect their desire of maintaining the mobility through automobiles because today’s 28

highway environment in most cases is based on the performance characteristics of the younger population. Therefore, it is necessary to identify the critical problems experienced by this population subset so that roadway facility performance and design standards can be improved. The safety of young drivers is of high concern in almost every country, but more severe problems may exist in the United States where licenses are generally allowed one to two years earlier than most other countries. Young drivers aged 15 to 24 are being injured and killed at an alarming rate. Among all age groups, young drivers are the most likely to be injured in crashes.2 Investigations need to be carried out to find the suitable design and policy changes that would help change this alarming trend and reduce its impact. International tourists play an important role in the U.S. tourism industry. Florida attracts a considerable percentage of international tourists. Out of the total 22 million international tourists that came to the United States in 1995, 19.2 percent were attracted to Florida.3 This group of highway users originates from countries all over the world. Significant differences exist between the transportation systems and signing practices used in these originating countries and in the United States. Although traffic signs are rather uniform in the United States, international tourists may not be able to correctly interpret or promptly respond to some traffic signs. 4 International tourists are obviously unfamiliar with the area in which they are driving, which may cause unfamiliar drivers to have different driving behavior to perceptionreaction, car following, lane change, gap acceptance, etc. In addition, they are unfamiliar with U.S. driving laws and customs as well. Thus, international tourists may have a higher potential to be involved in traffic-related incidents. ITE JOURNAL / SEPTEMBER 1999

Ensuring the safety of children en route to and from school is a growing public concern in the United States. According to a study conducted by the Center for Urban Transportation Research (CUTR) at the University of South Florida, approximately 10,600 motorists illegally pass stopped school buses in Florida during a typical school day.5 Based on a 180-day school year, this accounts for about 1.9 million motorists illegally passing stopped school buses during a typical school year. This alarming number of illegal passes along with other factors raises several broad and important issues about motorists not only in Florida but also in the whole country. New immigrants were identified as another special population group whose safety problem has received little or no attention. Immigrants are coming to the United States in record numbers, many of whom come from vastly different environments. For many immigrants, walking or bicycling is the only familiar mode of transportation. But still, they are not familiar even with these activities under very high vehicular volumes or speeds. Many immigrants, who do not have long-time exposure to safe driving habits, are forced to learn to drive for the first time. This learning process may be more difficult due to language barriers and cultural differences. Further, many new immigrants learn to drive from friends or family members who also lack experience. These barriers, differences and difficulties combine to create serious safety concerns for new immigrants, which need to be investigated through research. Full participation in the society by the people with disabilities is essential for their independent living, overall well being and economic sufficiency. It also saves societal costs, which would otherwise be used to take care of them. For this participation they require access to the transportation system not only in a barrier-free way but also in a safe manner. The Americans with Disabilities Act of 1990 increased access to public facilities for persons with disabilities. The safety problem of this population subset is of a different nature and requires careful consideration. Unique characteristics of certain special population groups such as those ITE JOURNAL / SEPTEMBER 1999

explained earlier have become an important issue to the highway-safety community. There is a huge potential to reduce the number of traffic crashes and hence the economic loss to the country by addressing the critical safety issues relevant to these subsets. This feature summarizes a research study to identify the critical special population groups and corresponding critical issues and concerns related to highway safety and recommends suitable countermeasures in addressing the identified issues. This research project was funded by the Southeastern Transportation Center (STC) at the University of Tennessee, which is part of the University Transportation Centers Program of the U.S. Department of Transportation. METHODOLOGY

In the structured decision-making process, the need to make value assessments and benefit measurements occurs at two points: in the specification of the relative importance of the goals and in the evaluation of the relative effectiveness of the alternatives.6 In this study, attention was focused on the first approach where the relative importance of special populations and their highway-safety issues were assessed. Out of the four different types of management science methods that exist for making that kind of assessment, a combination of rating/scoring and ranking methods was used. Even though a set of numbers (rating/scoring) were estimated through the surveys, they do not reflect a precise measurement or an exact meaning and were used only to obtain the rank-order numbers. Two surveys seeking expert opinions were conducted in this study to identify the critical population groups and to develop the final ranking among the identified critical issues and concerns under each group. Target population of the two surveys included traffic/transportation engineers, safety engineers, law-enforcement officers, administrative officers dealing with safety-related matters, university academics and Community Traffic Safety Team (CTST) members throughout Florida. Their compositions in responding to the surveys are listed in Table 1. The first survey

Table 1. Composition of survey respondents. Profession Engineers Law-enforcement officers Administrative officers University academics Others and unknown Total

Number (Percentage) Survey 1 Survey 2 52 (56.5%)

29 (40.3%)

13 (14.1%)

11 (15.3%)

11 (12.0%) 5 (5.4%) 11 (12%) 92 (100%)

7 (9.7%) 2 (2.8%) 23 (31.9%) 72 (100%)

was designed to gather preliminary data so that the critical groups could be identified. It also helped the research team get a feel for the importance of the issues and concerns faced by the groups. Out of the 149 survey forms that were sent out in the first survey, 92 were returned resulting in a response rate of 62 percent. The second survey was built based on the results of the first survey, which was a more detailed instrument, taking several different criteria into account. For the second survey, 164 forms were sent out and the response rate was 44 percent. The first page of the first survey form listed six special population groups, and respondents were asked to select one of the six choices for each group. The choices included one for “No Opinion” and others varied from 1 to 5, with 1 indicating “Least Important” and 5 indicating “Most Important.” The rest of the survey form listed the preliminary identified issues and concerns under each of the special population groups. Each issue/concern needed a simple check mark according to the opinion of the respondent depending on the importance, as in the case of special population groups. In addition, the respondents also were provided with the opportunity to indicate their views by adding any more subgroups or issues/concerns. The second survey addressed the issues and concerns of each group in detail. The possibility of making an evaluation or improvement about the issue also was taken into consideration while eliminating or adding some of the issues. Expert opinions were gathered under six different attributes, where they were requested 29

to put a check mark for each issue under each attribute based on a scale of 1 to 5. The attributes considered in the second survey included: 1. What impact do these issues have on crash/accident rates? (1–No Impact, 5–High Impact) 2. How effective would it be to use roadway design changes to address each of these issues? (1–Not Effective, 5–Highly Effective) 3. How effective would it be to use policy changes to address each of these issues? (1–Not Effective, 5–Highly Effective) 4. How costly would it be to implement a design or policy change to address each issue? (1–Not Costly, 5–Very Costly) 5. How easy would it be to implement the change? (1–Not Easy, 5–Very Easy) 6. How much of a priority to address each issue/concern? (1–Not a Priority, 5–High Priority) Both survey forms were faxed to the target group and follow-up phone calls were made with the expectation of having a high return rate. Since the second survey form required much more time and energy by the respondents, it was expected to have a lower return rate than the first one. As such, the second survey form also was mailed with a self-addressed, stamped envelope in addition to the faxed survey form. Even though this was expected to provide better flexibility for the respondents, response rate of the second survey was still smaller than that of the first survey. The final ranking model, which ranked the issues under each group, was developed by considering the responses to the second survey. Weights were assigned to each of the attributes based on the significance, and more accurate understanding about the critical safety issues was obtained by calculating an index for each issue. This index corresponds to a score that handles a multidimensional situation and estimates the weighted sum of all the attributes considered. Ranking of issues was obtained by considering the value of the index. The higher the index, the more importance was placed on the issue. For a given population group, the index for each issue was: 6

Ij =

∑W X i

i =1

30

ij

Table 2. Ranking of importance among selected population groups. Ranking 1 2 3 4 5 6

Special population group Older drivers School-age children Young drivers Disabled people International tourists New immigrants

where Ij = index for issue j; Wi = weight of the attribute i; Xij = mean response rating for issue j when considering attribute i; i = attributes being considered (1, 2, 3, 4, 5 and 6); and j = issues. One of the most important and also difficult steps in this procedure was to determine the weights. Two different approaches are available in selecting the weights: observer-derived and clientreplicated.7 However the first approach has not received much popularity due to the fact that the purpose of multicriteria decision models ought to improve on, not imitate, subjective choice.8 Clientreplicated approaches solicit the weights directly from the decision-makers and try to ensure that evaluations of alternatives are consistent and rational. Among the several different methods available under this category, this research used the rating method, where the weights were assigned judgmentally on the basis of a predetermined scale from 1 to 10. Weight of “1” indicated less importance of the attribute and “10” indicated very high importance. Weights were obtained by using two groups of experts and the average rating for each criterion was selected as the assigned weight. The ranking results using different sets of weights were compared to see the reliability of the outcome. The two approaches used to assign the weights included: (1) through a focus group, and (2) through the survey responses. The focus group in the first approach was the research team that assigned weights for each attribute, depending on their personal opinion on importance of

Mean rating

Standard deviation

4.28 4.12 4.00 3.53 3.35 3.12

1.07 0.87 1.01 1.23 1.28 1.06

the attributes. In this case, based on discussions and reviews by the research team, weights were assigned for attributes irrespective of the special population group and issues/concerns. The second approach was to use average rating for the attributes obtained from survey responses as the weight. This approach also enabled weights to be estimated for the attributes separately under each special population group. Thus, the two sets of weights estimated under the second approach included: (1) weights for attributes irrespective of the group and issue/concern, and (2) different weights for attributes under each special population group. All three sets of weights obtained using two approaches were used to calculate the index (Ij ) used in ranking, and the results were compared. RESEARCH FINDINGS

Ranking of importance among the selected special population subsets obtained by considering the mean ratings of the responses to the first survey is shown in Table 2. According to the responses, the group of older drivers who received a mean response rating of 4.28 out of 5 was the most critical group when considering highway safety among the selected groups. Second and third critical groups were identified as schoolage children and young drivers, followed by the other three groups, people with disabilities, international tourists and new immigrants. Using the ranking model explained earlier, the index (Ij ) was calculated for each and every issue under each special population group, and a ranking of importance in terms of highway safety was obtained, depending on the index ITE JOURNAL / SEPTEMBER 1999

Table 3. Development of ranking of issues for older drivers (using the focus group set of weights). Issues/concerns (j )

(1) w1 = 8.5

(2) w2 = 5

Attribute* (i ) (3) (4) w3 = 5 w4 = –6.5

(5) w5 = 6.5

(6) w6 = 3

Index 6

Ij =

∑W X i

ij

Ranking (order)

i=1

Nighttime visibility Driving in congestion Freeway driving Maneuvering curves Deficiencies in driving knowledge Location and size of traffic signs and lettering Perception-reaction time Gap acceptance Narrow lanes

4.3 3.9 3.0 3.2 2.8 3.6 4.3 4.2 3.2

3.2 2.5 2.5 3.1 1.9 3.8 2.8 2.8 3.4

2.8 2.3 2.2 2.2 2.9 3.3 2.3 2.4 2.9

3.8 4.1 3.7 3.8 2.8 3.6 3.2 3.3 4.0

2.5 2.5 2.7 2.4 3.0 3.2 2.2 2.5 2.3

3.7 3.1 2.6 2.8 3.4 3.6 3.3 3.0 3.1

69.2 56.05 50.3 53 59.3 74.3 65.75 65.5 56.95

2 7 9 8 5 1 3 4 6

*Cell values are the mean response ratings for each issue under each attribute, obtained from the responses to the second survey.

Table 4. Final ranking of critical highway-safety issues for all groups. Group Older drivers

Rank

1 2 3 4 5 6 7 8 9 School-age children 1 2 3 4 5 6 7 8 9 Young drivers 1 2 3 4 5 6 7 People with disabilities 1 2 3 4 International tourists 1 2 3 4 5 New immigrants 1 2 3 4 5

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Issues/concerns Location and size of traffic signs and lettering Nighttime visibility Perception-reaction time Gap acceptance Deficiencies in driving knowledge Narrow lanes Driving in congestion Maneuvering curves Freeway driving Lack of sidewalks and bike routes Lack of parental guidance Speeding in and around school zones Lack of traffic and bicycle safety programs Lack of drop-off and pick-up zones Lack of proper signage and traffic signals Lack of school crossing guards Lack of traffic calming devices High traffic volumes around schools Speeding Reckless/aggressive driving Impaired driving Lack of driving experience Lack of safety restraint use Lack of driver training programs Immaturity Lack of policies for issuing and recalling driver’s licenses Lack of standards for vehicle modifications required Unsafe access to transportation facilities Faulty designs in roadways and intersections Difficulty in recognizing and understanding traffic signs Lack of information about driving laws/customs in the United States Unfamiliar with roadway system Confusion in translating English into metric distance on signs Unfamiliar with driving system Unfamiliar with traffic laws and regulations Lack of safety education Unfamiliar with road systems Lack of driver education Unfamiliar with vehicle systems

magnitude. One of the results, the development of the rankings of the critical issues/concerns for older drivers, is illustrated in Table 3 by using the set of weights obtained through the focus group. The first attribute, impact on crash rates, has a weight (w1) of 8.5 out of the highest possible value of 10. Other weights of the attributes of this set of weights are given in the table. All the attributes except the fourth one have positive effects toward increasing the index and ranking. But if the cost associated with a design or policy change is very high, the ranking of the corresponding issue/concern tends to be lower. As such, w4 bears a negative sign whereas the other weights are positive. The cell values indicate mean response ratings for each issue under each attribute and were obtained by analyzing the responses to the second survey. Using these data, the index for each issue was obtained as the summation of the product of cell value and corresponding weight. Ranking of critical highway safety issues/concerns for older drivers using this set of weights was then obtained depending on the index magnitude. Location and size of traffic signs and lettering that received the highest index of 74.3 was ranked first and so on. A similar procedure was used in the case of the other two sets of weights obtained through the survey responses as explained earlier. However, the ranking results for older drivers and other special population groups based on the other two sets of weights were almost consistent with the ITE JOURNAL / SEPTEMBER 1999

Table 5. A summary of the suggested countermeasures. Older drivers • Special education programs to address specific needs of older drivers; • Physical therapies; • Age-based license renewal; and • Engineering improvements: Improved roadways (intersections), better highway sign visibility, better pavement markings, signal-timing improvements. School-age children • Engineering: School-zone speed control, intersection improvements, reduced pedestrian crossing distances; • Education: Changes to school-bus-driver curriculum and school-bus-stop law information; and • Enforcement: Citation of pedestrians for improper crossing, strict school-zone speed and school-bus passing enforcement. Young drivers • Overhaul of driver education curriculum; • Increased parental involvement in training; • Graduated licensing: Several steps to get full license, age-related curfew, age-related passenger restrictions, “zero” alcohol tolerance; and • Seat-belt promotion. People with disabilities • License recall for progressive disabilities; • Special adaptive equipment; • Special education targeting needs; and • Vehicle design modifications. International tourists • Use of international symbols; • Better destination markings; • More consistency of route numbers; • Use of diagrammatic signs; and • Information sessions/brochures. New immigrants • Education through families, churches, community groups and media; • Roadway sign changes; and • Improved data collection.

ranking developed by using weights through the focus group, indicating reliability of the outcome. Based on the three ranking orders, final ranking of critical highway safety issues/concerns for older drivers was obtained. Final rankings of the critical highway safety issues of the other special population groups were obtained in the same way as for older drivers, and all the findings are listed in Table 4. A ranking of “1” indicates the most important highway safety issue for that special population group. COUNTERMEASURES

In addition to the identification of the critical groups and issues, the study also 34

suggested suitable countermeasures to address each issue. The suggestions were made based on an extensive review of literature and current practices related to the methods of improving safety, close consultation with the relevant safety experts and engineering judgment. The potential changes were either in public policy or engineering practices. Countermeasure matrices were prepared for each special population group for better representation of the recommendations. However, some of the countermeasures can be effectively employed in addressing more than one critical safety issue identified through the surveys. A brief summary of the suggested countermeasures useful in

addressing the identified critical issues in relation with the highway safety problems of each of the special population group is given in Table 5. SUMMARY AND CONCLUSIONS

There is a huge potential of reducing the number of traffic crashes and hence the economic loss to the country by addressing the safety issues relevant to the special population groups considered in this research. In approaching this, it is necessary to fully understand the unique characteristics associated with each special population group and then to provide the appropriate guidelines to address the problem areas. This research was intended to fulfill that requirement. Rankings developed in this research can be used by decision-makers in transportation safety to decide which issues should be addressed first and in which way. Out of the six special population subsets considered in this study, the most critical special population group was identified as older drivers and the second critical group was school-age children as nonmotorists. Young drivers, people with disabilities and international tourists were the third, fourth and fifth critical groups, respectively, in terms of highway safety. Due to the warm tropical climate and recreational amenities, Florida attracts many special populations, including senior citizens, immigrants and tourists, and hence offered an excellent environment to examine the roadway safety issues in association with these subgroups. ■ References 1. Bureau of Transportation Statistics. Transportation Statistics Annual Report 1998. Washington, D.C., USA: U.S. Department of Transportation (USDOT), 1998. 2. National Highway Traffic Safety Administration. Crash Data and Rates for Age-Sex Groups of Drivers, 1996. Research Note. Washington, D.C., USA: USDOT, January 1998. 3. Florida Tourism Industry Marketing Corp. Florida Visitor Study, 1996. 4. Wilbur Smith Associates and Florida Department of Transportation. Evaluation of International Signing Practices, Volumes 1 and 2, November 1994. 5. Baltes, M.R. “Measuring Motorist Comprehension of Florida’s School Bus Stop Law ITE JOURNAL / SEPTEMBER 1999

and School Bus Signalization Devices.” TRB Preprint. Washington, D.C., USA: Transportation Research Board, January 1998. 6. Souder, W.E. Management Decision Methods for Managers of Engineering and Research. New York, N.Y., USA: Van Nostrand Reinhold Co., 1980. 7. Goicoechea, A., D.R. Hansen and L. Duckstein. Multiobjective Decision Analysis with Engineering and Business Applications. New York, N.Y., USA: John Wiley and Sons, 1982. 8. Hobbs, B.F. Analytical Multiobjective Decision Methods for Power Plant Siting: A Review of Theory and Applications. Upton, N.Y., USA: Division of Regional Studies, Brookhaven National Laboratory, August 1979.

SUNANDA DISSANAYAKE is a Graduate Research Associate at CUTR at the University of South Florida (USF). Since joining USF, she has been involved in transportation

ITE JOURNAL / SEPTEMBER 1999

research in the areas of highway safety, traffic operations and crash modeling. She holds an M.Eng. in civil engineering from the Asian Institute of Technology in Thailand and a B.Sc.(Eng.) from the University of Moratuwa in Sri Lanka. She is an Associate Member of ITE. JIAN JOHN LU, P.E., is an Associate Professor at the Department of Civil and Environmental Engineering at USF. His research interests cover traffic operations, highway safety, ITS and vehicle-pavement interaction. He holds a Ph.D. from the University of Texas at Austin, a master’s degree from Tongji University and a bachelor’s degree from the Beijing University of Science and Technology. He is a Member of ITE.

XUEHAO CHU is a Senior Research Associate with CUTR at USF. His research interests include quantitative methods and modeling, transportation economics, policy analysis and highway safety. He holds a Ph.D. from the University of California at Irvine and a B.S. from Hangzhou University in China. PATRICIA TURNER is a Senior Research Associate with CUTR at USF. She has been involved in highway-safety research related to motorcycle, bicycle and pedestrian issues and traffic-crash data for the past several years. She holds an M.P.A. from USF and a B.S. from the University of Maryland. Turner is a Member of ITE.

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