TRANSPORT AND EMERGENCY MEDICAL RESPONSE SYSTEMSA REVIEW OF THE IMPACT OF MEDICAL CARE ANDTECHNOLOGY IN REDUCING TRAFFIC FATALITIES
Robert B. NOLAND
Centre for Transport Studies
Department of Civil & Environmental Engineering
Imperial College London
London, UK(Received June 28, 2004)
Over the last 30-40 years dramatic improvements have been seen in the development of new methods for saving the lives of those involved intraffic crashes. This ranges from improvements in emergency medical response systems to advanced trauma care procedures to specific surgicalintervention techniques. This paper reviews the evidence for these improvements as documented in the safety and medical literature. The overall
impact on traffic fatalities has been examined in several recent studies that have attempted to examine these effects empirically using data from theUS, Great Britain, and international data from a selection of western countries. Overall results suggest impressive reductions in total fatalities whentrends in medical care and technology improvements are controlled. This has interesting implications for maintaining future reductions in fatalities
and the likelihood of attaining significant further improvements in many countries. In addition, analysts and policy makers should be aware of how
fatality reductions from these factors may affect analyses of traffic safety policies.
Key Words: Traffic safety, Medical technology, Health care, Emergency medicine, Negative binomial models

1. INTRODUCTION
Over the last 50 years developed industrializedcountries have largely become fully motorized with alarge proportion of daily travel being made by individuals using cars. At the same time that total travel has increased, fatality rates, whether measured per kilometre oftravel or on a per-capita basis, have generally decreased.
The reasons for this reduction are a result of specificpolicy measures taken to both increase the safety of thevehicle and to change the behaviour of individual drivers. This includes major improvements in the design ofvehicles, spurred by regulations, such that crashes are
more survivable; legislation to require the use of safetybelts; and increased attention and enforcement of laws on
drunk driving.
Less attention has been paid to reducing excessive
speeds, with the exception of traffic calming measures inresidential areas. Roadway design has also often been
mentioned as providing safety benefits, and while somedesign measures are likely beneficial, those that lead toincreased speeds are probably less effective1,2.
The other major factor that has contributed to decreased mortality in road vehicle accidents is changes inmedical care and technology. This includes a broad rangeof medical techniques, including development of emer-

6 • IATSS RESEARCH Vol.28 No.2, 2004

gency management and trauma care systems. The fatality reduction effects from these are likely quite substantial and a further understanding of these effects isbeneficial for at least two reasons. First, it provides aframework for understanding how to direct limited resources available for reducing traffic fatalities. Second,large reductions in fatalities due to medical technology
improvements may often distort the analyses of othersafety policies and may lead analysts to incorrectly conclude that some policies are more effective than they actually are.
This paper will provide an overview of some ofthese issues. A brief review of the medical literature isprovided that discusses the development of trauma caresystems and various life-saving technologies that havecontributed to reduced mortality from road crashes. An
overview of recent empirical research that has examinedthese issues is then provided. Finally, the implications
for policy makers as well as for those studying road safetyissues are provided.

2. REVIEW OF THE MEDICAL AND HEALTH
CARE LITERATURE
Mortality from road vehicle accidents has been considered a “disease of affluence”. That is, as general pros-

A REVIEW OF THE IMPACT OF MEDICAL CARE AND TECHNOLOGY IN REDUCING TRAFFIC FATALITIES

perity in society increases it leads to changes in the types
of factors associated with mortality3. In the case of motor-vehicle related fatalities, increasing affluence is associated with increased rates of motorization which leads
to an increasing level of fatalities. In most industrializedcountries there is a peaking of this effect, after which increasing affluence leads to a decrease in the level of fatalities. This same pattern has been found in analyses ofmortality from cardiovascular disease which is also considered a “disease of affluence” 4,5.
The long-term trend in traffic crash mortalities was
examined by van Beeck et al.3 using cross-sectional andtime series data from a selection of industrialized countries,
confirming this pattern. They found that for most countries, traffic-related mortalities increase until some critical level of income after which mortalities decrease. One
explanation for this effect is that both learning effects andthe introduction of policies to counteract a growing mortality problem are enacted, as countries become more affluent. Learning effects can include the development of
new methods of medical care and treatment of trauma,
while enactment of other policies in response to the increase in mortality, are also likely to be implemented.
Additional evidence for this effect was found byBester6. Using international road fatality data, fatality
rates were found to be associated with a Human Development Index that included Gross Domestic Product, life
expectancy, and educational levels. Beenstock and Gafni7
found correlations between crash rates in Israel and withan index of international crash rates. They hypothesizethat this may be due to a “globalization model” of roadsafety whereby technology transfer of vehicle and roadinfrastructure technology have led to decreases in fatalities in all industrialized countries. Oppe8 also hypothesized that learning effects can explain the downward
trend in traffic fatalities for developed countries. Clearly
medical care improvements could likewise disseminate
between countries. Slade and Anderson9 found that dissemination of new medical technologies is correlated withper-capita income, lending support to this theory.
There is good anecdotal evidence that the development of trauma systems and delivery of medical care forcrash victims follows this sort of pattern. The development of trauma systems was originally a by-product ofexperience gained in treating wounded soldiers datingback to at least World War I. Mullins10 and Trunkey11
both provide a historical overview of the development of
trauma care systems. The introduction of helicopter
evacuation of wounded soldiers during the Korean and
Vietnam wars was found to significantly reduce mortal-

R. B. NOLAND

ity rates, and this led to the use of helicopters for emergency medical transportation. In the mid-1960’s manyof the physicians with experience gained in the militarytransplanted these systems to civilian situations. Nathens
et al.12 point out that rapid movement of injured patients
to hospitals capable of effectively treating them is an essential component of trauma care.
The dissemination of new knowledge and the development of new surgical skills did not happen immediately. Nathens et al.13 find in an analysis of US data,that it took about 10 years to achieve the full benefit of a
trauma care system. Cutler and McClellan14 describe
how new medical technologies can be more effective, butthat much of the benefit results from the extension of newtechnologies to treat more patients as knowledge about
the effectiveness of treatments is disseminated. This isconsistent with the evidence that trauma system benefits
take time to accumulate.
Mullins10 describes the identification of public injury as a health problem, primarily due to a National Research Council15 report in 1966. In the US, this madethe issue a political one. This coincided with concern
over the design of vehicles and new regulations to improve crash-worthiness and survivability for occupants.
The political response led to initial funding of trauma systems in selected states via the National Highway Safety
Act of 196610.
While the development of comprehensive trauma
systems has clearly played a role in reducing traffic related fatalities, overall advances in medical care and technology have also been significant in this time frame.
Newhouse16 lists many of the advances that have occurred
over the last 40 years in the health sciences. These include items of physical capital, such as magnetic resonance imaging but also a variety of new procedures
ranging from transplantation to artificial joints to endoscopy. As evidence for the effectiveness of these practices, Newhouse16 examines hospital admission rates
which have not increased in line with an aging population. Average hospital in-patient stays have decreasedsuggesting that treatment techniques are more effective
and that many more can now be conducted on an outpatient basis. Another example is improvements in infant mortality rates over the last 40 years which are theresult of many life-saving technological interventions andimprovements in medical care17.
While these measures are not necessarily directly
associated with the trauma which occurs in traffic crashes,
they serve as an indicator of general advances in medical practices and technical abilities. Advances more diIATSS RESEARCH Vol.28 No.2, 2004 •7

TRANSPORT AND EMERGENCY MEDICAL RESPONSE SYSTEMS

rectly linked to traffic crashes include the treatment of
traumatic brain injury which has also undergone significant advances over the last 30 years. This includes theintroduction of clinical tools such as computed tomography (CT) scanners, which were introduced in the
1970’s18. Computer based storage systems for clinicalimages, radiographs, photographs, and ECGs have beendeveloped and implemented that help in teaching and research within accident and emergency departments19. In
the UK, telemedicine has also been applied to two major
areas of accident and emergency practice20. These are
the transmission of CT scans for urgent neurosurgery andthe ongoing support of minor injury units.
This review of recent literature builds a case that
medical interventions, either through technology improvements or systemic improvements such as trauma care systems, have significantly contributed to reductions inmotor-vehicle crash fatalities. Next, results from analyses of various databases that shed some further light onthese issues, especially in terms of the likely quantity oflives saved is reviewed and summarized.

3. REVIEW OF RECENT EMPIRICAL STUDIES
These issues have been analyzed in recent work using a variety of different databases by Noland1,21 andNoland and Quddus22. The data analyzed was from theUnited States, Great Britain, and international data froma selection of industrialized countries. In all cases, aggregate crash analysis models were developed. These
correlate total fatalities or injuries in a multivariate analysis of factors likely to be associated with changes in thosevariables. In addition, all the estimations used time-series cross-sectional data that enabled control for heterogeneity and changes in unmeasured factors over time.
This latter is critical to control for, as many other elements of the transport system have changed over time including vehicle design and other safety initiatives thatcannot be explicitly controlled.
To measure changes in medical care and technology, a variety of proxy variables were used. A review
of existing data sources found no clear guidance on thebest variables to represent these changes. Data availability limited what could practically be tested in the models. This also led to different proxy variables being tested
for different datasets, which provided additional robustness to the overall conclusions.
Most of the models estimated also used a fixed ef-

8 • IATSS RESEARCH Vol.28 No.2, 2004

fect negative binomial regression technique as specified
by Hausman et al.23. This method is appropriate for crosssectional time-series data. As the dependent variable isa count variable, one cannot assume that this data is normally distributed. Hausman’s method also controls forheterogeneity in the data. Noland and Karlaftis24 examined the need for using models for count data and concluded that these methods are most appropriate for thisdata.
Each of the three studies is reviewed and discussed
below.
3.1

Analysis of US data
In the US data white infant mortality rates wereused as the proxy variable to represent medical technology change. This was based on an assessment of thevariation in infant mortality rates over the time series ofthe data with a reduction of 34% nationwide between
1985 and 1997. This improvement has been documented
to be due primarily to medical technology improvements25. There was also substantial regional variation
between states, for example, in 1996 West Virginia had
a rate of 9.1 per 1000 births while New Hampshire had
a rate of 4.3. This variation in outcomes could be associated with relative affluence between states, and represent the dissemination of new medical care procedures.
White infant mortality rates were used to reduce the correlation between per capita income and total infant mortality rates1.
This variable was found to be statistically significant with the expected directional effect. As infant mortality rates improved, traffic related fatalities werereduced. This variable was not statistically significant
when models were estimated with total injuries as the dependent variable. Injuries would tend to be correlated
more strongly with overall crashes and be more affectedby policies aimed at reducing the incidence of crashes.
Therefore, we would not expect medical technology
changes to affect the incidence of total injuries, which
was confirmed by the estimation results. Finally, when
the white infant mortality variable was omitted from themodel, much of the residual effect was captured by thetime trend variable which was not statistically significant
when this variable was included. This suggests that muchof the residual change over time is being explained byunderlying changes in medical care and technology.
3.2

Analysis of British data
The analyses of these effects in British data again
used a cross-sectional time-series approach. Data on traf-

A REVIEW OF THE IMPACT OF MEDICAL CARE AND TECHNOLOGY IN REDUCING TRAFFIC FATALITIESfic fatalities and both serious and slight injuries were aggregated at the regional level based on the Standard Statistical Regions of the United Kingdom22. Three different
proxy variables were tested in the models estimated.
These included the average length of in-patient stay in thehospital, which has fallen over time and as Newhouse16
states is a good indicator of improvements in technology.
National Health Service (NHS) staff per capita and thenumber of people waiting for hospital treatment were also
included as proxy variables. These two variables would
serve to indicate the level of economic resources devoted
to health care. Much of the increase in economic resources devoted to health care has been devoted to technology as indicated by Newhouse16. This may include
the need for more labor, but not necessarily.
In a count model with total fatalities as the dependent variable, estimated with a negative binomial regression, these variables have the expected effect. Average
length of hospital in-patient stays are positively associated with fatalities. This means that as there has been a
reduction in average length of in-patient stay (due to technology improvements) there has also been a reduction in
total fatalities. More NHS staff per capita was negatively
associated with total fatalities (significant above the 85%
confidence level). This means that as staff per capita
numbers increase there is a reduction in total fatalities.
Wa™iting times for hospital treatment are positively associated with total fatalities. Again, this is a resource issue and as more resources are devoted to medical carewe would expect waiting times to decrease and we would
expect a reduction in fatalities.
Effects on all of these variables are different in the
injury models (i.e., with serious injuries and slight injuries as the dependent variable). This suggests an inherent difference in the association of these variables withfatalities as opposed to injuries. It could represent a shift
from crashes resulting in fatalities to more serious injuries, as survivability increases.
An additional analysis was conducted in Noland
and Quddus22 that examined the association of theseproxy variables with a ratio of fatalities to slight injuries.
As the evidence suggested some shifting between classes
of injuries over time, we would expect these variables tobe strongly associated with this ratio. Over time the fraction of total injuries that are fatal has been declining.
Since the dependent variable is no longer a count variable an ordinary least squares estimation using a fixed
effects method which further allowed for a correction for
autocorrelation in the data was applied. In this model, it
was found that the medical technology and care proxy

R. B. NOLAND

variables had the highest level of statistical significance(all above the 90% confidence level), while many of theother variables in the model were at a relatively lower
level of statistical significance and much lower than in
the count model estimates. The results were as expected,
showing the proxy variables to have the expected direction which was the same as in the total fatality countmodel (i.e., average length of in-patient hospital stays was
positive, NHS staff per-capita was negative, and numberof persons waiting for hospital treatment was positive).
This result, again adds reinforcing evidence for a strong
effect from medical care and technology improvements.
3.3

Analysis of international data
Noland21 performed an analysis using international
data from a selection of industrialized countries from theOrganization for Economic Cooperation and Development (OECD). A number of different models were estimated with and without various proxy variables for
medical technology improvements. These proxies included, infant mortality rates, physicians per capita, andaverage acute care days spent in the hospital. These aresimilar to the variables used in the previous two studies
and were obtained from OECD Health Care data.
The most robust result was found for average acutecare days in the hospital. This should be more closely
associated with medical technology changes than the average in-patient days in the hospital used in the British
analysis. The relatively higher coefficient value foundin this analysis (0.36 – 0.50) compared to the British
study (0.28 – 0.32) suggest a stronger association, which
would be expected. A similar result was found for thephysicians per capita variable which was also highly significant and robust across different model specifications.
The coefficient value ranged from -0.24 to -0.27 compared to -0.09 to -0.14 in the British analysis. This again
should be more strongly associated with improvements
in medical care (especially more specialized care) as opposed to total medical staff increases. Infant mortality
rates were not found to be statistically significant andwere also highly correlated with per capita income in thisdata. When per capita income was removed from themodel and infant mortality was the only medical technology proxy variable included, then it had the expected signand level of significance.
3.4

Overall fatality reductions
The overview of these studies provides good evidence that improvements in medical care and technology
has been a factor in reducing traffic fatalities. A key
IATSS RESEARCH Vol.28 No.2, 2004 •9

TRANSPORT AND EMERGENCY MEDICAL RESPONSE SYSTEMS

question is how substantive an effect this has been.
Noland1 and Noland and Quddus22 report results on
how the changes in the proxy variables over time have
led to changes in total fatalities using elasticity calculations. Using the US data set, Noland1 concluded that
2,047 fewer fatalities would have resulted in 1985 if thetechnology of 1997 were available then. This would result in 4.5% fewer fatalities in 1985. This actually exceeds the reduction of 1,847 fatalities between 1985 and1997. The British analysis shows a reduction of between
640 and 726 fatalities, based on the coefficient for average in-patient stays in the hospital. This would accountfor up to one-third of the 2,100 fewer fatalities between
1979 and 1998 (note that this data excludes fatalities for
London and Scotland).
Further analysis of the international data is shownin Table 1. The total fatalities for 1970 and 1996 areshown for the OECD countries listed. Based upon parameter estimates from Noland21 that were estimated withlogarithmic independent variables and thus can be used

as elasticity values, and based upon the changes in theproxy variables we get a large range for the potential reduction due to medical technology improvements. Table
1 shows the reductions that would have occurred in 1970
if 1996 technology had existed in that year. These range
from 9,708 to 35,847 fewer total fatalities from thesecountries. This reduction would be from a total of
142,636 traffic fatalities in 1970, therefore representing
anywhere from 6.8% to 25.1% of the total.
While the potential range shown here is quite large,
the implication is clear that medical care and technology
improvements have had a major effect on overall reductions in fatalities in the last 40 years. A good consensus
estimate based on the results of the studies above is thatbetween 5% and 25% of the reductions in fatalities in thistime frame are due to improvements in medical care andtechnology, which includes trauma and emergency response systems. The implications for future policy associated with reducing traffic fatalities in the next section
are discussed.

Table 1 Changes in fatalities based upon parameter estimates from international data analysis
Country

Total fatalities
1970

Total fatalities
1996

Reduction based on
infant mortality
parameter

Reduction based on
physicians per capita
parameter

Reduction based on
average acute care daysin hospital parameter

Australia

3,798

1,970

-262

-1,011-379

Austria

2,574

1,027

-211

-633

-453

Belgium

3,070

1,356

-224

-956

-589

Canada

5,080

3,092

-353

-499

-380
-232

Denmark

1,208

514

-78

-318

Finland

1,055

404

-75

-547

-229

France16,4458,541-1,005-4,975-3,876

Greece

1,099

2,157

-99

-388

NA

Ireland

540

453

-40

-100

-99

Italy

11,025

6,688

-904

-10,840

-472

Japan

21,795

11,674-1,578-3,409NA

Luxembourg

132

71

-11

-32

-14

Netherlands

3,181

1,180

-192

-782

-576

New Zealand

655

514

-37

-146

NA

Norway

560

255

-39

-138

-119

Portugal

1,615

2,394

-144

-926

-289

Spain

5,456

5,483

-451

-2,992-91-264

Sweden

1,307

537

-85

-445

Switzerland

1,643

616

-115

-519

-121

UK

7,771

3,740

-531

-441

-1,466

US

52,62742,065-3,274-5,749-4,033

Total

142,636

94,731-9,708-35,847-13,680-6.81%-25.13%

Percent of total

10 • IATSS RESEARCH Vol.28 No.2, 2004

-9.59%

A REVIEW OF THE IMPACT OF MEDICAL CARE AND TECHNOLOGY IN REDUCING TRAFFIC FATALITIES

4. IMPLICATIONS FOR POLICIES TO REDUCEFATALITIES
These results have important implications for our
understanding of how best to further reduce traffic-related
fatalities. As the review and the empirical data suggests,
medical care and technology improvements have been
substantial over the last 30-40 years and this knowledge
has been put to good use in reducing overall traffic-related fatalities.
One implication of this work is that it may change
our understanding of the effectiveness of other policy interventions. A significant body of research has documented the effectiveness of wearing safety-belts, reducing
drunk driving, reducing speed limits, and changing vehicle design and infrastructure design. Many of these initiatives have occurred concurrently with the changes inmedical care and technology. The difficulty for analysts
is to clearly disentangle the effects of the various mechanisms, something that is not always done.
Much of the statistical analyses of traffic crashes
has not accounted for many of these confounding factors
and has often not used the most current statistical techniques2. This situation is improving as count data estimation methods become more widespread. Many studies
also do not attempt to disentangle the effects on fatalities as opposed to injuries or total crashes. As Noland
and Quddus22 showed, the impact of medical technologies on fatalities is not the same as the impact on injuries. Clearly one limitation of many studies is that dataon fatalities may be sparse or non-existent while injury
or crash data is more abundant.
The problem (for analysts, but not for motorists) ofsparse data sets of fatalities leads to the use of time-series analysis in before and after studies. If the time-series stretches over more than a few years, then trend
reductions in fatalities need to be controlled for. Medical care and technology improvements may account formuch of this trend reduction, and excluding some control for the trend can distort conclusions as to whether
the policy or intervention being studied is effective.
As medical care and technology has improved dramatically over the last 40 years, a relevant question iswhether this trend will continue. Eng26 outlines numerous possibilities for further technology improvements inmedicine. Cutler and McClellan14 document the cost-effectiveness of past improvements, suggesting that further
improvements are clearly worth the investment. If trends
do not continue, it may be difficult to achieve further ma-

R. B. NOLAND

jor reductions in crash fatalities, without other policy interventions. These are then probably best focussed on
reducing crash rates and the severity of crashes when theyoccur.
If further technical change in medical care and technology can improve survivability rates and this is desirable from a public policy perspective, then this has
implications for the funding of road crash reduction programs. As Mullins10 documented, in the US the implementation of trauma care systems received a boost fromFederal funding. Continued funding and incentives todevelop and improve technology and disseminate newknowledge may be more effective at reducing fatalities
than other crash reduction programs. Current knowledge
can not answer this question, but clearly this should beof priority for further research in this area.

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