Th¡s pro¡ect sought to determine the effectiveness of vârious low-cost countermeasures for reduc¡... more Th¡s pro¡ect sought to determine the effectiveness of vârious low-cost countermeasures for reduc¡ng the number of fixed ob¡oct and overturn¡ng crashes. A survey was conducted of the 50 state highway and transportation departments. Responses to the qusst¡onnaire show that all rtates are using chevron markers, and a ma¡or¡ty are using delineators and standard warning signs. Respondsnts thought that th€ss devicss were most effective for reducing run.off.the.road crashes, although l¡ttls documen-tat¡on was suppl¡ed to support this contention. Most states have established procedures for select¡ng the most hazardous run-off-the-road sites, but few have formal guidelines for selscting the specific countermeasuros for use at these sites. A crit¡cal analysis is needed to determ¡ne the actual effectiveness of several commonly used low-cost @untormoasuros.
A recent paper on the concepts underlying six indexes of severity that have been proposed for hea... more A recent paper on the concepts underlying six indexes of severity that have been proposed for health services research claimed to identify deficiencies in each. A close examination reveals that the criticisms are generally without substance, and that the claim that the indexes "violate some of the principles implied by their formulation" is in error. Most of the objections apparently stem from fundamental confusion concerning the use of such indexes. Two of the indexes in question, the Abbreviated Injury Scale AIS) and the Injury Severity Score (ISS), have been validated and are being used widely both in the United States and elsewhere as the principal descriptors of trauma in motor vehicle crashes. The use of these indexes has contributed significantly to motor vehicle crash research and to the improvements in vehicles and highways that are reducing the trauma resulting from such crashes.
Ite Journal-institute of Transportation Engineers, Mar 1, 1983
This article reports the results of a study based on a random sample of sharp curves in Georgia t... more This article reports the results of a study based on a random sample of sharp curves in Georgia that were treated by the installation of raised and recessed reflectorized pavement markers. The random sample of study sites is representative of sites in moderate to warm climates where there is relatively little exposure to snow and ice removal operations. Results show that: (1) Recessed pavement markers outlast raised pavement markers by a factor of two or more under similar conditions; and (2) Over 95 percent of the recessed pavement markers remained in place for over five years on roads with up to an ADT of 4,700.
PROCEEDINGS OF THE 16TH INTERNATIONAL CONFERENCE ON ALCOHOL, DRUGS AND TRAFFIC SAFETY, 2002
Although license suspension/revocation is considered to be one of the more effective countermeasu... more Although license suspension/revocation is considered to be one of the more effective countermeasures for alcohol-impaired driving, many alcohol offenders whose licenses have been suspended/revoked as a result of convictions for driving under the influence/while intoxicated (DUI/DWI) continue to drive illegally and go undetected. The current study evaluated the deterrent effect of a novel sting operation on Maryland drivers whose licenses had been suspended/revoked following an alcohol-related offense. We further investigated whether repeat sting operations in the same city confer added benefits. (A) For the covering abstract of the conference, see ITRD Abstract No. E201067.
Ite Journal-institute of Transportation Engineers, Nov 1, 1980
The study described was conducted to determine how intersection conflict frequency depended on ye... more The study described was conducted to determine how intersection conflict frequency depended on yellow signal time duration at two suburban arterial intersections under different traffic and environmental conditions. The findings of this study apply to the pretimed traffic signals.
Deeply tinted window glass transmits less light than less deeply tinted glass and therefore reduc... more Deeply tinted window glass transmits less light than less deeply tinted glass and therefore reduces driver visibility. Research was conducted to investigate the extent to which reduced levels of luminous (or light) transmittance in automobile windows are associated with decreased visibility of the kind of low and medium contrast objects that are likely to be seen in the roadway to the rear of passenger cars. The task of looking through the rear window for hazards before backing a car was simulated in a laboratory setting. Five targets (car, bicyclist, pedestrian, child, and debris) were shown to drivers from three age groups (18-55, 56-75, 76+) under conditions representing various combinations of luminous transmittance of the windows and luminance (brightness) contrast of the targets. The frequency of correct target detection was analyzed. The results varied by target. The car was always detected; however, detection probability decreased with reduced luminous transmittance for the child and roadway debris targets. For the bicyclist, pedestrian, child, and debris targets, detection probability decreased with lower luminance contrast and for older groups. The results of this experimental study, conducted under simulated conditions that were less demanding than real driving conditions, suggest that the safety of backing maneuvers is compromised for all drivers at the lowest luminous transmittance (darkest tinting) levels studied, and this is particularly so for elderly drivers for tinting levels darker than the 70% minimum luminous transmittance required by Federal Motor Vehicle Safety Standard 205.
A MAJOR change in the types of motorcycles used on public roads oc- 16 curred in California and e... more A MAJOR change in the types of motorcycles used on public roads oc- 16 curred in California and elsewhere during the 1980s with the introduc- tion and marketing for street use of high performance motorcycles designed for racing. The first racing design models appeared in dealers' showrooms in 1981. Since then, more radical racing designs have been introduced, such as the Honda Interceptor series in 1983 and the Kawasaki Ninja and Yamaha FJ series in 1984. This new type of motorcycle was patterned after those used in competition track races. These motorcycles have been marketed with adver- tising emphasizing high speed, rapid acceleration, and aerodynamic styling. The introduction of this new type of motorcycle coincided with an unusually large increase in the motorcycle fatality rate in California from 1983 to 1986.1 The overall objective of this study was to compare motorcycle-crash injury rates for different types of motorcycles in California. Rates of fatal and severe nonfatal injury motorcycle crashes, according to model type, were ascertained to determine crash injury rates for specific groups of motorcycles characterized by design category and performance class. METHODS
the Global Slavery Index of the Walk Free Foundation. She was recently named the 2016 Statistical... more the Global Slavery Index of the Walk Free Foundation. She was recently named the 2016 Statistical Advocate of the Year by the American Statistical Association and as a Forbes Top 30 Under 30 in Science in 2017 for her work on statistical modeling, human security theory, and human trafficking. She applies analytical models to understanding vulnerability, risk, and prevalence of human trafficking domestically and internationally.
, the Georgia Department of Transportation installed reflectorized pavement markers on the center... more , the Georgia Department of Transportation installed reflectorized pavement markers on the centerlines of nearly 700 curves in Georgia which had horizontal curvature in excess of six degrees. Nighttime crashes were reduced by about 20 percent compared to daytime crashes at these sites subsequent to the installation of the markers. Nighttime single-vehicle crashes were reduced more than other nighttime crashes.
Special truck rollover-warning signs were examined for effectiveness in slowing tractor-trailer t... more Special truck rollover-warning signs were examined for effectiveness in slowing tractor-trailer trucks to a speed below that associated with rollover on highway exit ramps. Advisory speeds were verified for trucks at three highway exit ramps with high truck rollover crash frequencies; rollover-warning signs specific to trucks were posted to supplement the standard speed advisory signs already in place. The supplemental rollover-warning sign was equipped with a yellow light that was triggered to flash for every second tractor-trailer truck traveling above a predetermined ramp approach speed. Mean speeds at midramp associated with the flashing sign were lower than for the nonflashing sign. Although the flashing signs did not significantly increase the number of trucks in strict compliance with maximum safe speeds, they did significantly reduce the number of trucks that were traveling more than 5 mph and 10 mph faster than the calculated maximum safe speed. These findings suggest that speed-actuated rollover advisory signs specific to trucks may reduce truck rollover crashes at highway ramps.
Model-based relative driver involvement risk and risk confidence bound estimates for two vehicle ... more Model-based relative driver involvement risk and risk confidence bound estimates for two vehicle crashes by BAC, sex, and age, using zero BAC as the baseline. Data from the 96NRS and FARS, years 95-96 .
The purpose of this experiment was to determine a) the magnitude of alcohol impairment of driving... more The purpose of this experiment was to determine a) the magnitude of alcohol impairment of driving skills as BACs varied from zero to 0.10% and b) whether age, gender, and drinking practice characteristics of the subjects would differentially affect alcohol impairment in a sample of subjects who were broadly representative of the driving population. Using a driving simulator and a divided attention task, 168 subjects were examined at BACs to 0.10% for moderate and heavy drinkers and to 0.08% for light drinkers. Alcohol significantly impaired performance on some measures at all examined BACs from 0.02% to 0.10%. The magnitude of the impairment increased with increasing BAC. Differences in the magnitude of alcohol impairment between categories of age, gender, and drinking practices were small, inconsistent in direction, and did not reach statistical significance. It is possible that significant differences would have emerged if a wider range of subject characteristics and BACs had been examined. BACs over 0.10% were not tested, and the sample did not include subjects under 19 years and over 70 years, or very light and very heavy drinkers. Within those limits, no significant differences in the magnitude of alcohol impairment within the categories of age, gender, and drinking practice appeared for this diverse sample.
ABSTRACT Alternative analyses of data previously published by Zador et al. confirm that adoption ... more ABSTRACT Alternative analyses of data previously published by Zador et al. confirm that adoption of right-turn-on-red laws increased by about 18% the frequency of all right-turning crashes at all signalized intersections in the jurisdictions that adopted such laws. From a view of the available literature it is estimated that at the approximately 80% of all signalized intersections where motorists are allowed to turn right on red all right-turning crashes increased by about 23%, pedestrian crashes by about 60%, and bicyclist crashes by about 100%. 11 references, 1 table.
The relationship between the results of the National Highway Traffic Safety Administration's ... more The relationship between the results of the National Highway Traffic Safety Administration's (NHTSA's) New Car Assessment Program (NCAP) and the risk of fatal injury to drivers involved in fatal frontal collisions between passenger cars of similar weights were examined. The results are based on the Fatal Accident Reporting System (FARS) data for the years 1975-1983 analyzed by individual make and model of car. The risk of fatality was modelled using logistic regression taking into account the effect of the combined weight and weight ratio of the two cars, the ages of both drivers, restraint use by both drivers, speed limit at the site of the crash, the number of occupants in the car, and the NCAP test results for each individual model of car. The results show that when the other factors were controlled the likelihood of a fatal driver injury was almost 60 percent higher for cars with the worst NCAP results than for cars with the best results.
PROCEEDINGS OF THE 16TH INTERNATIONAL CONFERENCE ON ALCOHOL, DRUGS AND TRAFFIC SAFETY, 2002
Alcohol-impaired driving legislation and sanctions have historically been aimed at the offender w... more Alcohol-impaired driving legislation and sanctions have historically been aimed at the offender with multiple driving while intoxicated (DWI) convictions, with little or no attention paid to the first-time offender or to alcohol-related events other than DWI [such as administrative per se (APS) violations involving breath alcohol content (BrAC) of 0.10 or more, APS breath test refusal and probation before judgment (PBJ)]. It is a widely held belief among the legislature and judicial branches of state government that first offenders criminally convicted of an alcohol related traffic law are drivers with a single and isolated alcohol-related violation that results in arrest. This finding is inconsistent with published estimates that a person can drive while impaired by alcohol 200 to 2,000 times before being arrested once for alcohol-impaired driving (1-6). Moreover, some drivers manage to have their records expunged under certain conditions, and many state motor vehicle administration (MVA) offices routinely purge driving records after a set number of years. Therefore, it is reasonable to assume that the typical so-called first-time offender will have had an extensive history of alcohol-impaired driving by the time he or she makes it into the MVA's record system. The current research examines the relative risk of alcohol-related recidivism among drivers with one, two and three or more alcohol-related events (not just convictions) and expands prior research (7) using an updated data set. Our findings suggest that first-time alcohol-related traffic offenders are at a high and significant risk of reoffending even after one alcohol-related event and that alcohol-impaired driving recidivism among first offenders more closely resembles that of multiple alcohol offenders. The results demonstrate that any alcohol-related traffic event (APS BrAC of 0.10 or more, APS breath refusal, and PBJ), not just convictions, should be perceived by the courts, the MVA, and physicians as a marker for future alcohol-related recidivism. The results also suggest that relative risk among females is similar to the risk among males once females have had one alcohol-related event. For the covering abstract of the conference, see ITRD Abstract No. E201067
Th¡s pro¡ect sought to determine the effectiveness of vârious low-cost countermeasures for reduc¡... more Th¡s pro¡ect sought to determine the effectiveness of vârious low-cost countermeasures for reduc¡ng the number of fixed ob¡oct and overturn¡ng crashes. A survey was conducted of the 50 state highway and transportation departments. Responses to the qusst¡onnaire show that all rtates are using chevron markers, and a ma¡or¡ty are using delineators and standard warning signs. Respondsnts thought that th€ss devicss were most effective for reducing run.off.the.road crashes, although l¡ttls documen-tat¡on was suppl¡ed to support this contention. Most states have established procedures for select¡ng the most hazardous run-off-the-road sites, but few have formal guidelines for selscting the specific countermeasuros for use at these sites. A crit¡cal analysis is needed to determ¡ne the actual effectiveness of several commonly used low-cost @untormoasuros.
A recent paper on the concepts underlying six indexes of severity that have been proposed for hea... more A recent paper on the concepts underlying six indexes of severity that have been proposed for health services research claimed to identify deficiencies in each. A close examination reveals that the criticisms are generally without substance, and that the claim that the indexes "violate some of the principles implied by their formulation" is in error. Most of the objections apparently stem from fundamental confusion concerning the use of such indexes. Two of the indexes in question, the Abbreviated Injury Scale AIS) and the Injury Severity Score (ISS), have been validated and are being used widely both in the United States and elsewhere as the principal descriptors of trauma in motor vehicle crashes. The use of these indexes has contributed significantly to motor vehicle crash research and to the improvements in vehicles and highways that are reducing the trauma resulting from such crashes.
Ite Journal-institute of Transportation Engineers, Mar 1, 1983
This article reports the results of a study based on a random sample of sharp curves in Georgia t... more This article reports the results of a study based on a random sample of sharp curves in Georgia that were treated by the installation of raised and recessed reflectorized pavement markers. The random sample of study sites is representative of sites in moderate to warm climates where there is relatively little exposure to snow and ice removal operations. Results show that: (1) Recessed pavement markers outlast raised pavement markers by a factor of two or more under similar conditions; and (2) Over 95 percent of the recessed pavement markers remained in place for over five years on roads with up to an ADT of 4,700.
PROCEEDINGS OF THE 16TH INTERNATIONAL CONFERENCE ON ALCOHOL, DRUGS AND TRAFFIC SAFETY, 2002
Although license suspension/revocation is considered to be one of the more effective countermeasu... more Although license suspension/revocation is considered to be one of the more effective countermeasures for alcohol-impaired driving, many alcohol offenders whose licenses have been suspended/revoked as a result of convictions for driving under the influence/while intoxicated (DUI/DWI) continue to drive illegally and go undetected. The current study evaluated the deterrent effect of a novel sting operation on Maryland drivers whose licenses had been suspended/revoked following an alcohol-related offense. We further investigated whether repeat sting operations in the same city confer added benefits. (A) For the covering abstract of the conference, see ITRD Abstract No. E201067.
Ite Journal-institute of Transportation Engineers, Nov 1, 1980
The study described was conducted to determine how intersection conflict frequency depended on ye... more The study described was conducted to determine how intersection conflict frequency depended on yellow signal time duration at two suburban arterial intersections under different traffic and environmental conditions. The findings of this study apply to the pretimed traffic signals.
Deeply tinted window glass transmits less light than less deeply tinted glass and therefore reduc... more Deeply tinted window glass transmits less light than less deeply tinted glass and therefore reduces driver visibility. Research was conducted to investigate the extent to which reduced levels of luminous (or light) transmittance in automobile windows are associated with decreased visibility of the kind of low and medium contrast objects that are likely to be seen in the roadway to the rear of passenger cars. The task of looking through the rear window for hazards before backing a car was simulated in a laboratory setting. Five targets (car, bicyclist, pedestrian, child, and debris) were shown to drivers from three age groups (18-55, 56-75, 76+) under conditions representing various combinations of luminous transmittance of the windows and luminance (brightness) contrast of the targets. The frequency of correct target detection was analyzed. The results varied by target. The car was always detected; however, detection probability decreased with reduced luminous transmittance for the child and roadway debris targets. For the bicyclist, pedestrian, child, and debris targets, detection probability decreased with lower luminance contrast and for older groups. The results of this experimental study, conducted under simulated conditions that were less demanding than real driving conditions, suggest that the safety of backing maneuvers is compromised for all drivers at the lowest luminous transmittance (darkest tinting) levels studied, and this is particularly so for elderly drivers for tinting levels darker than the 70% minimum luminous transmittance required by Federal Motor Vehicle Safety Standard 205.
A MAJOR change in the types of motorcycles used on public roads oc- 16 curred in California and e... more A MAJOR change in the types of motorcycles used on public roads oc- 16 curred in California and elsewhere during the 1980s with the introduc- tion and marketing for street use of high performance motorcycles designed for racing. The first racing design models appeared in dealers' showrooms in 1981. Since then, more radical racing designs have been introduced, such as the Honda Interceptor series in 1983 and the Kawasaki Ninja and Yamaha FJ series in 1984. This new type of motorcycle was patterned after those used in competition track races. These motorcycles have been marketed with adver- tising emphasizing high speed, rapid acceleration, and aerodynamic styling. The introduction of this new type of motorcycle coincided with an unusually large increase in the motorcycle fatality rate in California from 1983 to 1986.1 The overall objective of this study was to compare motorcycle-crash injury rates for different types of motorcycles in California. Rates of fatal and severe nonfatal injury motorcycle crashes, according to model type, were ascertained to determine crash injury rates for specific groups of motorcycles characterized by design category and performance class. METHODS
the Global Slavery Index of the Walk Free Foundation. She was recently named the 2016 Statistical... more the Global Slavery Index of the Walk Free Foundation. She was recently named the 2016 Statistical Advocate of the Year by the American Statistical Association and as a Forbes Top 30 Under 30 in Science in 2017 for her work on statistical modeling, human security theory, and human trafficking. She applies analytical models to understanding vulnerability, risk, and prevalence of human trafficking domestically and internationally.
, the Georgia Department of Transportation installed reflectorized pavement markers on the center... more , the Georgia Department of Transportation installed reflectorized pavement markers on the centerlines of nearly 700 curves in Georgia which had horizontal curvature in excess of six degrees. Nighttime crashes were reduced by about 20 percent compared to daytime crashes at these sites subsequent to the installation of the markers. Nighttime single-vehicle crashes were reduced more than other nighttime crashes.
Special truck rollover-warning signs were examined for effectiveness in slowing tractor-trailer t... more Special truck rollover-warning signs were examined for effectiveness in slowing tractor-trailer trucks to a speed below that associated with rollover on highway exit ramps. Advisory speeds were verified for trucks at three highway exit ramps with high truck rollover crash frequencies; rollover-warning signs specific to trucks were posted to supplement the standard speed advisory signs already in place. The supplemental rollover-warning sign was equipped with a yellow light that was triggered to flash for every second tractor-trailer truck traveling above a predetermined ramp approach speed. Mean speeds at midramp associated with the flashing sign were lower than for the nonflashing sign. Although the flashing signs did not significantly increase the number of trucks in strict compliance with maximum safe speeds, they did significantly reduce the number of trucks that were traveling more than 5 mph and 10 mph faster than the calculated maximum safe speed. These findings suggest that speed-actuated rollover advisory signs specific to trucks may reduce truck rollover crashes at highway ramps.
Model-based relative driver involvement risk and risk confidence bound estimates for two vehicle ... more Model-based relative driver involvement risk and risk confidence bound estimates for two vehicle crashes by BAC, sex, and age, using zero BAC as the baseline. Data from the 96NRS and FARS, years 95-96 .
The purpose of this experiment was to determine a) the magnitude of alcohol impairment of driving... more The purpose of this experiment was to determine a) the magnitude of alcohol impairment of driving skills as BACs varied from zero to 0.10% and b) whether age, gender, and drinking practice characteristics of the subjects would differentially affect alcohol impairment in a sample of subjects who were broadly representative of the driving population. Using a driving simulator and a divided attention task, 168 subjects were examined at BACs to 0.10% for moderate and heavy drinkers and to 0.08% for light drinkers. Alcohol significantly impaired performance on some measures at all examined BACs from 0.02% to 0.10%. The magnitude of the impairment increased with increasing BAC. Differences in the magnitude of alcohol impairment between categories of age, gender, and drinking practices were small, inconsistent in direction, and did not reach statistical significance. It is possible that significant differences would have emerged if a wider range of subject characteristics and BACs had been examined. BACs over 0.10% were not tested, and the sample did not include subjects under 19 years and over 70 years, or very light and very heavy drinkers. Within those limits, no significant differences in the magnitude of alcohol impairment within the categories of age, gender, and drinking practice appeared for this diverse sample.
ABSTRACT Alternative analyses of data previously published by Zador et al. confirm that adoption ... more ABSTRACT Alternative analyses of data previously published by Zador et al. confirm that adoption of right-turn-on-red laws increased by about 18% the frequency of all right-turning crashes at all signalized intersections in the jurisdictions that adopted such laws. From a view of the available literature it is estimated that at the approximately 80% of all signalized intersections where motorists are allowed to turn right on red all right-turning crashes increased by about 23%, pedestrian crashes by about 60%, and bicyclist crashes by about 100%. 11 references, 1 table.
The relationship between the results of the National Highway Traffic Safety Administration's ... more The relationship between the results of the National Highway Traffic Safety Administration's (NHTSA's) New Car Assessment Program (NCAP) and the risk of fatal injury to drivers involved in fatal frontal collisions between passenger cars of similar weights were examined. The results are based on the Fatal Accident Reporting System (FARS) data for the years 1975-1983 analyzed by individual make and model of car. The risk of fatality was modelled using logistic regression taking into account the effect of the combined weight and weight ratio of the two cars, the ages of both drivers, restraint use by both drivers, speed limit at the site of the crash, the number of occupants in the car, and the NCAP test results for each individual model of car. The results show that when the other factors were controlled the likelihood of a fatal driver injury was almost 60 percent higher for cars with the worst NCAP results than for cars with the best results.
PROCEEDINGS OF THE 16TH INTERNATIONAL CONFERENCE ON ALCOHOL, DRUGS AND TRAFFIC SAFETY, 2002
Alcohol-impaired driving legislation and sanctions have historically been aimed at the offender w... more Alcohol-impaired driving legislation and sanctions have historically been aimed at the offender with multiple driving while intoxicated (DWI) convictions, with little or no attention paid to the first-time offender or to alcohol-related events other than DWI [such as administrative per se (APS) violations involving breath alcohol content (BrAC) of 0.10 or more, APS breath test refusal and probation before judgment (PBJ)]. It is a widely held belief among the legislature and judicial branches of state government that first offenders criminally convicted of an alcohol related traffic law are drivers with a single and isolated alcohol-related violation that results in arrest. This finding is inconsistent with published estimates that a person can drive while impaired by alcohol 200 to 2,000 times before being arrested once for alcohol-impaired driving (1-6). Moreover, some drivers manage to have their records expunged under certain conditions, and many state motor vehicle administration (MVA) offices routinely purge driving records after a set number of years. Therefore, it is reasonable to assume that the typical so-called first-time offender will have had an extensive history of alcohol-impaired driving by the time he or she makes it into the MVA's record system. The current research examines the relative risk of alcohol-related recidivism among drivers with one, two and three or more alcohol-related events (not just convictions) and expands prior research (7) using an updated data set. Our findings suggest that first-time alcohol-related traffic offenders are at a high and significant risk of reoffending even after one alcohol-related event and that alcohol-impaired driving recidivism among first offenders more closely resembles that of multiple alcohol offenders. The results demonstrate that any alcohol-related traffic event (APS BrAC of 0.10 or more, APS breath refusal, and PBJ), not just convictions, should be perceived by the courts, the MVA, and physicians as a marker for future alcohol-related recidivism. The results also suggest that relative risk among females is similar to the risk among males once females have had one alcohol-related event. For the covering abstract of the conference, see ITRD Abstract No. E201067
Uploads
Papers by Paul Zador