Integrated Transport and Health Impact Modelling Tool (ITHIM)
ITHIM refers to a range of related models and tools developed at CEDAR to perform integrated assessment of the health effects of transport scenarios and policies at the urban and national level. The health effects of transport policies are modelled through the changes in physical activity, road traffic injury risk, and exposure to fine particulate matter (PM2.5) air pollution. Some versions of ITHIM also predict changes in CO2 emissions. ITHIM is being used in research and by health and transport professionals to estimate the health impacts of scenarios, compare the impact of travel patterns in different places, and model the impact of interventions. ITHIM works either as a stand-alone model, or it can be linked with other models (e.g. transport, health, economic).
Figure 1: The general overview of the ITHIM model. Picture is from ITHIM version 2 (see version description below). Arrows show the flow of data inside the mode. (PM = fine particulate matter air pollution, GBD = Global Burden of Disease study).
ITHIM models exposure to physical activity by comparing distributions of weekly physical activity under different scenarios. Walking, cycling and other types of physical activity are combined as MET hours per week of activity. Outcomes affected by physical activity include various cardiovascular diseases, depression, dementia, diabetes, breast cancer, and colon cancer. ITHIM also models health changes through the all-cause mortality. A comparative risk assessment method is used to estimate how changes in population physical activity result in changes in health burden.
Road traffic injuries are modelled using a risk, distance and speed based model. Differences in risk by gender and age are also included. This approach allows ITHIM to look at how absolute numbers of injuries and injury risks could change for different transport modes as travel distances between modes changed.
Fine particulate matter (PM2.5) air pollution risks are calculated for the general population (background rates) as well as mode specific rates for different transport modes. The exposure changes for population are based on comparison of local generated PM2.5 emissions and concentrations in the study area. In ITHIM version 2 also the personal exposure to air pollution while walking and cycling is taken into account.
The health effects of ITHIM are presented as disability-adjusted life-years (DALY) and number of attributable deaths. Background burden data for study areas are estimated from Global Burden of Disease studies.
Below are listed the main ITHIM versions and key studies that have been published with those versions.
- ITHIM 1: First version of ITHIM was implemented as a spreadsheet model in Microsoft Excel. ITHIM version 1 had all three pathways (physical activity, injuries and air pollution). Physical activity variation between people was modelled with simple point estimate approach. ITHIM 1 has been used to model scenarios for the UK and the USA (Woodcock et al. 2009, 2013, Maizlish et al. 2013).
- ITHIM 1 for California: ITHIM for California is developed by Dr Neil Maizlish and is used to predict benefits of climate mitigation strategies of shifting commuter travel from personal passenger vehicles to walking and bicycling and/or to electric vehicles and biofuels (low carbon driving). See more here:
- ITHIM 2: The second version of ITHIM was developed to take better into account uncertainties and variability in key input data in the calculation. ITHIM version 2 was implemented with Analytica software (http://en.wikipedia.org/wiki/Analytica_%28software%29) and the uncertainty & variability was modelled by using Monte Carlo simulation. Key publication is the London cycle hire paper published in 2014 .
- ITHIM 3: The third version of ITHIM is under development in R in collaboration with the University of Wisconsin and other partners. The code base is hosted here and here . In the METAHIT project we developing ITHIM 3 for England.
- ITHIM Global: In the TIGTHAT project we are laying the foundations for a health impact assessment tool that will be readily applied to a wide variety of urban settings in Low or Middle Income Countries to estimate health impacts of transport choices.
- Impacts of Cycling Tool (ICT): The ICT generates scenarios using individual level travel survey data and we will include this functionality within ITHIM 3. The code base is available here
We are moving towards making all our models open source. Other models are available on request.
ITHIM related projects
We are collaborating on many international research and policy collaborations involving ITHIM these include:
- USA: Global Health Institute, University of Wisconsin-Madison
- USA: Nashville, Tennessee, Nashville Metropolitan Planning Organization
- USA: Portland, Oregon Department for Public Health
- Malaysia: Kula Lumpur, United Nations University – International Institute for Global Health
- Canada: Newfoundland University
- Brazil: Sao Paulo, University of Sao Paulo.
- USA: California, Center for Climate Change and Health, Public Health Institute
- India: Delhi and Visakhapatnam, Indian Institute of Technology, Delhi
ITHIM email list and ITHIM community
ITHIM is currently used by several researchers and authorities in number of cities, regions and countries (including USA, Canada, Malaysia, Brazil, India). ITHIM email list is the list in which developers of ITHIM will share the news from ITHIM community with other users and interested parties. We expect to send one email every 2-3 months.
A summary of a recent small survey of ITHIM users and developers is available here ithim_survey
Woodcock J, Edwards P, Tonne C, Armstrong BG, Ashiru O, Banister D, et al. 2009. Health and Climate Change 2 Public health benefits of strategies to reduce greenhouse-gas emissions: urban land transport. Lancet 374:1930–1943.
Woodcock J, Givoni M, Morgan AS. 2013. Health impact modelling of active travel visions for England and Wales using an Integrated Transport and Health Impact Modelling Tool (ITHIM). PLoS One 8; doi:10.1371/journal.pone.0051462.
Maizlish N, Woodcock J, Co S, Ostro B, Fanai A, Fairley D. 2013 Health cobenefits and transportation-related reductions in greenhouse gas emissions in the San Francisco Bay area. American Journal of Public Health 103(4):703-9.
Woodcock J, Tainio M, Cheshire J, O’Brien O, Goodman A. 2014. Health effects of the London bicycle sharing system: health impact modelling study. BMJ 348:g425.
Gotschi T, Tainio M, Maizlish N, Schwanen T, Goodman A, Woodcock J. Contrasts in active transport behaviour across four countries: How do they translate into public health benefits? Prev Med doi:10.1016/j.ypmed.2015.02.009