Epidemiology, cost and prevention of road traffic crash injuries in Strathclyde, Scotland

Jeffrey, Susanne K.E. (2010) Epidemiology, cost and prevention of road traffic crash injuries in Strathclyde, Scotland. PhD thesis, University of Glasgow.

Abstract

Background
Road traffic crash (RTC) injuries affect 20 to 50 million people worldwide every year, causing premature death or disability as well as incurring large costs to individuals and society. In the UK, the number of RTC casualties is underestimated if based solely on police records, as many casualties are unreported to the police. “Safety” (speed and red light) cameras have shown to be an effective way of combating RTCs and in 2000 a national scheme was rolled out in the UK.

Aim and objectives
The overall aim of the study was:
To investigate the epidemiology, cost and prevention of RTC injuries in the Strathclyde police region of Scotland.
The specific objectives of the study were:
1. To establish the overall epidemiology and accuracy of reporting of RTC injuries in Strathclyde.
2. To determine the epidemiology of RTC injuries and the effectiveness of safety cameras at the camera sites in Strathclyde with special reference to different road users, RTC types and severity, before and after camera installation.
3. To estimate the economic burden of hospital admissions due to RTC injuries in Strathclyde and at the camera sites before and after installation.

Methods
Nine years (1997 to 2005) of police road casualty records (STATS19) and National Health Service hospitalisation records (SMR01) from the Strathclyde region were linked.
The linkage resulted in nearly 11,000 police casualty records relating to approximately 30,000 hospital and death records. Unlinked RTC hospital and police casualties (nearly 9,000 and 70,000 respectively) were also utilised in the analysis.
The study employed a range of epidemiological and economic methods. These included descriptive epidemiology (evaluating distributions of linked and unlinked records, length of stay and cost analysis), analytical epidemiology (examining associations using chi square and logistic regression models) and interventional epidemiology (before and after study). The economic evaluation utilised weighted mean costs.
The focus of analysis was threefold: 1. Epidemiology of RTC, injuries and accuracy of police recording, 2. Epidemiological impact of safety cameras, 3. Cost of road traffic crashes a) in Strathclyde and b) at safety camera sites.

Results
Epidemiology of RTC injuries in Strathclyde: Older age and less protected road users (i.e. pedestrians and two-wheeled vehicle users) had a higher risk of a more severe outcome in RTCs. Head injuries were more common among pedestrians and pedal cyclists, while car occupants more often suffered injuries to the thorax and abdomen/lower back/lumbar spine.
Accuracy of police reporting: 45% of RTC hospital admissions were not recorded by police. Casualty characteristics significantly associated with underreporting were: no third party involvement, older age, casualties from early in the study period, type of road user (especially pedal cyclist), hospitalisation as a day case and female gender.
Seriously injured casualties recorded by police (STATS19) declined in frequency more than the RTC hospitalised injuries (SMR01) (38% and 21% respectively). Linked SMR01 casualties that were coded “slight” by the police increased by 5% over time, while linked SMR01 casualties coded “serious” declined by 27%.
Safety camera impact: Compared to the rest of Strathclyde, there was a significantly greater downward linear time trend of RTC incidence at the camera sites. The impact of cameras on RTCs over time appeared stable. Cameras seemed to be effective in reducing the incidence of serious or fatal RTC injuries, as well as injuries associated with multiple-vehicle and non-junction RTCs.
Cost of RTC casualties in Strathclyde: Total inpatient costs were conservatively estimated at £7.3 million yearly (linked records). Head and lower extremity injuries incurred the highest total costs (28% and 34% respectively). Pedestrian injuries, constituting 36% of the total, incurred 44% of total costs. Casualties from deprived areas, and pedestrians in particular, incurred higher hospital costs than other road user groups.
Cost of RTCs at safety camera sites: 17% of all injured before safety camera installation were hospitalised, while 13% of casualties after installation were hospitalised. The mean costs of (surviving) casualties admitted to hospital declined by 24% after installation and the mean daily cost declined by 55%.

Conclusions
RTC injury incidence in Strathclyde declined over the study period, which is in line with expectations of developed countries. Young and elderly people as well as unprotected road users carry a disproportionately great RTC injury burden.
Many hospitalised RTC casualties were not recorded by police and there appears to have been an increasing tendency over time for police officers to report injuries as slight rather than serious. National (UK) statistics of RTCs should be interpreted with caution in the light of these findings and routinely linking police and hospital data would enhance the quality of RTC casualty statistics. Linking police and hospital RTC records provide a more comprehensive source for road traffic analysis than any of the sources separately. Routine data linkage would also facilitate the evaluation of time trends in relation to national road casualty reduction targets.
The study indicates that the most costly RTCs occur in areas with high levels of deprivation, a history of pedestrian RTCs, elderly and child casualties, roads with many non-junction RTCs and 30 mph speed limits.
The evaluation of safety cameras strongly suggests that they are effective in reducing both road casualty incidence and severity and that the reduction in incidence is sustained over time. Additionally, safety cameras in Strathclyde may have contributed to a saving of over £5 million. Cameras thus fulfil an important public health, as well as law enforcement, function and should continue to play a central role in traffic calming.
This study has demonstrated the value of utilising multiple data sources in the road traffic injury field.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Epidemiology, injuries, road traffic crash, safety cameras, speed, cost, casualty, police records, hospital records, reporting, SMR01, Stats19
• Subjects: R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Stone, Prof. David H.
• Date of Award: 2010
• Depositing User: Mrs Susanne K E Jeffrey
• Unique ID: glathesis:2010-1448
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 05 Feb 2010
• Last Modified: 10 Dec 2012 13:40
• URI: https://theses.gla.ac.uk/id/eprint/1448