September 11, 2001 National Parameter, U.S. Interstate Roads and Highways (Reference Guide)

FARS does not provide an estimate of total traffic flow for a suitable denominator. It is, of course, spurious reasoning to associate this injury trend with attitudes toward terrorism. But it is also possible that these findings are suggestive of a trope in popular risk perception. An understudied, but oft-theorized, aspect of the mental-health impact of terrorism is the probability that pre-existing psychiatric conditions, especially those that are vulnerable to emotional stress, are likely to be exacerbated.

It is conceivable that these effects may include poor decision-making when it comes to risk perception and the choice of long-distance travel modes, possibly even manifesting in dangerous driving behavior. It is evident that risk perception is based more on qualitative and emotional factors than on more objective information, such as statistical assessments of safety.

Therefore, the responsibility of public-health workers is to develop strategies for proper and persuasive communication of true risk in an environment of agitated emotions. Gigerenzer suggested that it is enough to simply educate the public about the psychological nature of terror threats. While awareness of risk increases fear of it, 5 there is a danger in using that fact to reflexively deny the public knowledge of the true risk. The long-term safety statistics of various modes of travel suggest that it is irrational to avoid flying for fear of being among the very small proportion of people who die in airplane incidents, whether terror related or not.

Our analyses further suggest that such irrational behavior may in fact increase the risk of injury or death. But, as stated by Huddy et al, 12 it may be emotionally sensible to make these seemingly irrational decisions because doing so avoids the arousal of fearful emotions, which are themselves damaging. What is clear is that in a new era of large-scale threats to public safety, the health impact of risk perception is felt not just in the immediacy of a disaster, but long term in the form of both mental-health issues and poor decision-making. It falls to public health to improve its risk communication and management strategies.

Numbers of fatalities and injuries resulting from motor vehicle crashes from September 12—31, in , , and ; New York State 4. Numbers of fatalities and injuries resulting from motor vehicle crashes from September 12—31, in , , and ; combined data for Virginia and the District of Columbia 4. National Center for Biotechnology Information , U. Int J Gen Med. Published online Oct 1. Raywat Deonandan and Amber Backwell. Author information Copyright and License information Disclaimer.

This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited. Results While the fatality rate did not change appreciably, the number of less severe injuries was statistically higher in than in , both nationally and in New York State.

Conclusions The fear of terror attacks may have compelled Americans to drive instead of fly. Introduction In the weeks and months immediately following the New York and Washington terror acts of September 11, , millions of Americans decreased their domestic air travel. Results Tables 1 — 5 summarize the number of car-crash fatalities and injuries reported during the last 20 days of September in , , and , for the country as a whole, New York, Pennsylvania, California and the combined regions of Virginia and the District of Columbia.

Table 1 Numbers of fatalities and injuries resulting from motor vehicle crashes from September 12—31, in , , and ; USA National Data 4. Open in a separate window. Table 4 Numbers of fatalities and injuries resulting from motor vehicle crashes from September 12—31, in , , and ; Pennsylvania 4. Table 5 Numbers of fatalities and injuries resulting from motor vehicle crashes from September 12—31, in , , and ; California 4. Year Fatalities Incapacitating injuries 48 66 57 Fatal injuries Possible or non-incapacitating injury, or injury with severity unknown Table 3 Numbers of fatalities and injuries resulting from motor vehicle crashes from September 12—31, in , , and ; combined data for Virginia and the District of Columbia 4.

Year Fatalities 98 Incapacitating injuries 34 43 24 Fatal injuries 45 58 48 Possible or non-incapacitating injury, or injury with severity unknown 6 10 Footnotes Disclosure The authors report no conflicts of interest in this work. Tourism in the 21st century. US Department of Transportation. National Transportation Safety Board. Compressed Mortality File — Dealing with the dangers of fear: Health Aff Millwood ; 21 6: Do we fear the right things?

Dread risk, September 11, and fatal traffic accidents. National Highway Traffic Safety Administration. All states and the District of Columbia were eligible for inclusion if they 1 had both rural and urban interstates, 2 did not change rural interstate speeds between the starting point for our data collection and November , and 3 made changes to speed limits uniformly across the entire state's road system or within the state's functional road type. The District of Columbia, Massachusetts, and Hawaii did not meet the inclusion criteria.

The District of Columbia has no interstate highways. Massachusetts was the only state to change its rural interstate speed limits between and , which affected our stratification by speed limits. Hawaii raised its rural interstate speed limits on only 2 sections of road H-1 and H In addition, these 2 sections in Hawaii had posted speed limits of 60 mph; all the other states had speed limits of 65 mph or higher on rural interstates. All the other interstates in Hawaii retained a maximum speed limit of 55 mph.

We considered several aspects of the fatality data in choosing our statistical methods: For studies of trends in road injuries, we had to take into account changes in speed limits that occurred at different times. We sought a model that considered the different starting points for the intervention raised speed limits and the differences between and within states. Therefore, we selected a mixed-regression model with a Poisson distribution.

This statistical approach explicitly models a state's change across time by including random effects to account for the variation that occurred in each state separately. Unlike more traditional approaches, the mixed-regression model was much more flexible in handling repeated measures because it did not require the same number of observations for each state. More important, we were able to treat interventions as time-varying events, rather than as uniform for all states. Because the mixed-regression model allowed us to use the actual time changes, it provided a more accurate analysis of change associated with an intervention.

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By using annual data instead of monthly counts, we removed the effects of seasonality and focused on long-term trends. We also included time as a variable in our model to control for overall trend. Because the speed limits changed at different times in different states, we coded time as described by Hedeker and Mermelstein.

Introduction

The intervention variable was coded as a binary variable 0, 1 because we were interested in the cumulative effect of the increased speed limits. The year the change occurred and all subsequent years were coded 1, and all previous years were coded as 0. Annual exposure density and vehicle density were calculated for each state. The final mixed-regression model included time trend , intervention effect, exposure density, vehicle density, and rural speed limit. The rural speed limit was a categorical variable in which the expansion with no change states were the reference group.

A random state effect was included to account for the state effect.

Long-Term Effects of Repealing the National Maximum Speed Limit in the United States

We reported the parameter estimate for the intervention variable, which represented the mean change controlling for variance between states. A 2-sided P value less than. We also estimated the number of deaths and injuries attributable to the raised speed limits by multiplying the total number of cases after states raised their speed limits by the parameter estimate of the intervention variable in the model. The total number of cases was the number of deaths or injuries in fatal crashes occurring in each state after that state raised its speed limit on rural interstate roads.

A total of fatalities and injuries in fatal crashes occurred on all roads in the United States after states raised their rural interstate speed limits. On all road types combined, the average number of deaths annually in each state increased from The crude average annual number of injuries in fatal crashes increased by 4. Table 1 shows the percentage change attributable to increased speed limits by road type.

According to our mixed-regression analysis, the increase in road fatalities in the United States attributable to the raised speed limits was 3. The highest increase in fatalities was observed on rural interstates 9. In addition, injuries in fatal crashes increased by 3. All Poisson mixed-regression models included a random intercept for the state effect and the following fixed effects: Models included data for fatalities and injuries for to Massachusetts, Hawaii, and Washington, DC, were excluded.

When we stratified by change in speed limits, states that did not raise their speed limits after November showed a significant —8.

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The highest observed increase in fatalities attributable to raised speed limits occurred in states that had mph posted limits prior to and 65 mph later Table 2. All Poisson mixed-regression models included time trend, intervention, exposure density, and vehicle density as fixed effects and a random intercept for the state effect; models were calculated separately for each speed group.

Table 2 also shows the effect of changes to urban interstate speed limits. The only significant increase in deaths occurred in states that did not change their posted urban interstate speeds States that raised speed limits on rural interstates experienced significant increases in injuries in fatal crashes on rural noninterstate roads. However, casualties in fatal crashes rose in all states, irrespective of the change in maximum permitted speed limits.

Ours was the first evaluation of the sustained impact of raised speed limits across the United States following the repeal of the National Maximum Speed Law in We estimated that higher speed limits across the United States led to 12 excess deaths since the end of An alternative explanation for our findings would require major changes in driving under the influence, reductions in seat belt use, major failures in trauma care which have been recognized to affect case fatality as well as changes in other variables such as age, education, and income to account for the Newtonian relationship between speed and road deaths.

However, during the period of our study, to , we observed implementation of numerous protective countermeasures that may have reduced the overall effect of the rise in speed limits, including increased seat belt use, 34 , 35 more rigorous child restraint laws and increased child restraint use, 36 mandatory dual front air bag laws passed in , 37 , 38 and enforcement of driving while intoxicated laws, which led to minor declines in the number of drunk drivers involved in fatal crashes.

The largest increases in both fatalities and injuries in fatal crashes occurred on rural and urban interstate roads. These road types were the main locus of raised speed limits, although some states raised speed limits on segments of rural noninterstate roads as well. The small but significant increases in fatalities and injuries on all rural noninterstate roads were most plausibly attributable to the higher speed limits instituted on these roads as well as spillover from rural interstates.

However, the true direction of the change in deaths on rural noninterstate roads was uncertain. But when we stratified by speed Table 2 , we found no significant increase in fatalities. The only significant change was a substantial decline in states that made no change to their speed limits. States that made no change to their posted speed limits but expanded the number of rural interstate roads included under the preexisting mph speed limits expansion with no change group experienced significant declines in fatalities and injuries.

We suggest that the de facto travel speeds were already 65 mph across all rural interstates roads in these states prior to the legal change. These states are in fact the control group for the experiment of raised speed limits, and it is plausible that the decline in deaths observed in the no change states would have been mirrored in all other states had those states not increased their speed limits. Similar disparities between posted limits and de facto travel speeds were observed after rural interstate speeds increased from — from 55 to 65 mph.

Travel speeds after that change increased on average only 2 to 3 mph despite a mph increase in the legal limit. Although the posted speed limits were higher in the latter states, the actual change in travel speeds was probably greater in the states that raised speed limits from 55 to 65 mph. Nilsson found a fourth-power relationship between increases in travel speeds and increases in deaths 5 ; from this we estimated that travel speeds on rural interstates increased by 3.

We suggest that the lower overall change in fatalities and injuries on the higher-speed roads means not that higher travel speeds are safer but that the relative increase in travel speeds was less extreme on these roads. Speed adaptation and spillover effects occur when drivers coming off high-speed roads continue to drive faster than those already on the same road. Speed spillover from higher-speed roads is a plausible explanation for this finding. Australia, France, and the United Kingdom are countries with posted highway speed limits that are higher than those in many US states, but European Union countries have national speed management policies, enforce lower speeds, and maintain separate lanes for heavy vehicles.

Driving deaths and injuries post-9/11

The FARS database has several limitations. FARS does not collect information on crashes occurring on private property, such as private roads. FARS also only reports deaths that occur within 30 days of an accident. Furthermore, information on injuries occurring in fatal crashes is gathered predominately from police reports, which have been shown to be flawed in identifying severity of injury and to underreport injuries. Our data included only injuries occurring in fatal crashes. Nearly all injuries resulting from motor vehicle crashes occur in crashes that do not result in a death.

All of these limitations would contribute to an underestimation of the true effect of higher speed limits. Because of their uniqueness, we excluded Massachusetts and Hawaii from our analysis. Neither state's roads fit within our 4 interstate categories. Furthermore, a random state effect was included in the mixed-regression model to account for the state effect.

A class variable with only 1 state would not be appropriate for mixed-regression modeling and would require an alternative modeling procedure. It is probable that excluding Massachusetts and Hawaii resulted in a underestimation of the effect of raised speed limits on the traffic death toll in the United States. The failed policy of increased speed limits accounted for the deaths of an estimated 12 Americans over 10 years of follow-up. The repeal of the National Maximum Speed Law and its aftermath show that policy decisions that appear harmless can have long-term repercussions.

Our data support reinstating lower speed limits on rural and urban highways. Reduced speed limits would save lives; they would also reduce gas consumption, cut emissions of air pollutants, save valuable years of productivity, and reduce the societal cost of motor vehicle crashes. Lower legal speed limits and improved enforcement through the use of speed cameras could reduce travel speeds and fatalities immediately. National Center for Biotechnology Information , U. Am J Public Health. Author information Article notes Copyright and License information Disclaimer. Correspondence should be sent to Lee S.

Reprints can be ordered at http: Accepted December 29, This article has been cited by other articles in PMC. We divided the states into the following 4 categories for our analysis of rural roads: Expansion with no change. Increase of 10 mph only after November Expansion and 5 mph increase. Expansion and 10 mph increase. Inclusion Criteria All states and the District of Columbia were eligible for inclusion if they 1 had both rural and urban interstates, 2 did not change rural interstate speeds between the starting point for our data collection and November , and 3 made changes to speed limits uniformly across the entire state's road system or within the state's functional road type.

Statistical Analysis We considered several aspects of the fatality data in choosing our statistical methods: Open in a separate window. Interstate Roads When we stratified by change in speed limits, states that did not raise their speed limits after November showed a significant —8. Therefore, we stratified urban interstate roads into 3 groups by the legal speed limits after the National Maximum Speed Law was repealed.

Conclusions The failed policy of increased speed limits accounted for the deaths of an estimated 12 Americans over 10 years of follow-up. Human Participant Protection No protocol approval was needed for this study. Urban Transportation Planning in the United States: US Department of Transportation; Simple models of fatality trends revisited seven years later.

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Accid Anal Prev ; Speed, road injury and public health. Annu Rev Public Health ; The effect of speed limits on traffic accidents in Sweden. Organisation for Economic Co-operation and Development; Traffic Safety and the Driver. Van Nostrand Reinhold; A Decade of Experience.

National Research Council; Transportation Research Board Special Report Oxford University Press; Freedman M, Williams AF. Speed associated with 55 mph and 65 mph speed limits in northeastern states. Instit Transportation Engineers J ; Effects of the 65 mph speed limit on injury morbidity and mortality.