The objective of this study was to evaluate the time saved by usage of lights and siren (L&S) during emergency medical transport and measure the total number of time-critical hospital interventions gained by this time difference.

A retrospective study was performed of all advanced life support (ALS) transports using lights and siren to this university emergency department during a three-week period. Consecutive times were measured for 112 transports and compared with measured transport times for a personal vehicle traveling the same day of the week and time of day without lights and siren. The time-critical hospital interventions are defined as procedures or treatments that could not be performed in the prehospital setting requiring a physician. The project assessed whether the patients received the hospital interventions within the average time saved using lights and siren transport.

The average difference in time with versus without L&S was -2.62 minutes (95% CI: -2.60− -2.63, paired t-test p <0.0001). The average transport time with L&S was 14.5 ±7.9 minutes (min) (1 standard deviation/minute (min), range = 1–36 min.). The average transport time without L&S was 17.1 ±8.3 min (range = 1−40 min). Of the 112 charts evaluated, five patients (4.5%) received time-critical hospital interventions. No patients received time-critical interventions within the time saved by utilizing lights and siren. Longer distances did not result in time saved with lights and siren.

Limiting lights and siren use to the patients requiring hospital interventions will decrease the risks of injury and death, while adding the benefit of time saved in these critical patients.

Emergency medical services collisions (EMVCs) are a largely unexplored area of emergency medical services (EMS) research. Factors that might contribute to an EMVC are numerous and include use of warning lights and siren (WL&S). Few of these factors have been evaluated scientifically. Similarly, the incidence and severity of EMVCs is poorly documented in the literature. This study sought to define the incidence and severity of, and where possible, identify any contributing factors to EMVCs in a large urban system.

Retrospective study of all collisions involving vehicles assigned to the EMS Division of the Houston Fire Department in calendar year 1993. Fifty-one ambulances were operational 24 hours per day during calendar year 1993. Houston EMS received 150,000 requests for assistance, made 180,000 vehicular responses, and accrued 2,651,760 miles in 1993.

Eighty-six EMVCs were identified during the study period. The gross incidence rate was therefore 3.2 EMVC/100,000 miles driven or 4.8 collisions/10,000 responses. Of the 86 EMVCs, 74 (86%) files were complete and available for evaluation. Major collisions, determined according to injuries or vehicular damage, accounted for 10.8% of all EMVCs. There were 17 persons transported to hospitals from EMS collisions, yielding an injury incidence of 0.64 injuries/100,000 miles driven or 0.94 injuries/10,000 responses. There were no fatalities. The majority of collisions (85.1%) occurred at some site other than an intersection. There was no statistical association between occurrence at an intersection and severity, day versus night, weekend versus weekday, presence or absence of precipitation, or use of WL&S versus severity of collision. Drivers with a history of previous EMVCs were involved in 33% of all collisions. The presence of prior EMVCs was associated (p < 0.001) with the number of persons transported from the collision to a local hospital. Five drivers, all with previous EMVCs, accounted for 88.2% (15/17) of all injuries.

A few drivers with previous EMVCs account for a disproportionate number of EMVCs and nearly 90% of all injuries. This risk factor—history of previous EMVC—has not been reported in the EMS literature. It is postulated that this factor ultimately will prove to be the major determinant of EMVCs. Data collection of EMS collisions needs to be standardized and a proposed collection tool is provided.