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The Impact of Precipitation on Land Interfacility Transport Times

Published online by Cambridge University Press:  04 November 2014

Wayne C. W. Giang
Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
Birsen Donmez*
Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
Mahvareh Ahghari
Ornge, Mississauga, Ontario, Canada
Russell D. MacDonald
Ornge, Mississauga, Ontario, Canada Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
Correspondence: Birsen Donmez, PhD Department of Mechanical and Industrial Engineering University of Toronto 5 King's College Road Toronto, Ontario, Canada, M5S 3G8 E-mail



Timely transfer of patients among facilities within a regionalized critical-care system remains a large obstacle to effective patient care. For medical transport systems where dispatchers are responsible for planning these interfacility transfers, accurate estimates of interfacility transfer times play a large role in planning and resource-allocation decisions. However, the impact of adverse weather conditions on transfer times is not well understood.


Precipitation negatively impacts driving conditions and can decrease free-flow speeds and increase travel times. The objective of this research was to quantify and model the effects of different precipitation types on land travel times for interfacility patient transfers. It was hypothesized that the effects of precipitation would accumulate as the distance of the transfer increased, and they would differ based on the type of precipitation.


Urgent and emergent interfacility transfers carried out by the medical transport system in Ontario from 2005 through 2011 were linked to Environment Canada's (Gatineau, Quebec, Canada) climate data. Two linear models were built to estimate travel times based on precipitation type and driving distance: one for transfers between cities (intercity) and another for transfers within a city (intracity).


Precipitation affected both transfer types. For intercity transfers, the magnitude of the delays increased as driving distance increased. For median-distance intercity transfers (48 km), snow produced delays of approximately 9.1% (3.1 minutes), while rain produced delays of 8.4% (2.9 minutes). For intracity transfers, the magnitude of delays attributed to precipitation did not depend on distance driven. Transfers in rain were 8.6% longer (1.7 minutes) compared to no precipitation, whereas only statistically marginal effects were observed for snow.


Precipitation increases the duration of interfacility land ambulance travel times by eight percent to ten percent. For transfers between cities, snow is associated with the longest delays (versus rain), but for transfers within a single city, rain is associated with the longest delays.

GiangWCW, DonmezB, AhghariM, MacDonaldRD. The Impact of Precipitation on Land Interfacility Transport Times. Prehosp Disaster Med. 2014;29(6):1-7.

Original Research
Copyright © World Association for Disaster and Emergency Medicine 2014 

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