g loss of work output, and also of pollution in terms of health service costs for treatment for bronchial disorders, etc. The impacts of road accident costs on overall health costs, and on the total percentage of beds and care taken up by road accidents, might also shrink in a telecommuting model. However, telecommuting is spreading only slowly in OECD countries in knowledge worker based economic sectors and it is likely that this slow growth will to continue. According to the International Telework Association, the number of employed Americans who performed any kind of work from home, with a frequency range from as little as 1 day a year to full-time, grew from 41.3 million in 2003 to 44.4 million in 2004, a 7.5% growth rate. 76 Another survey expects 51 million US teleworkers in 2008 with about 14 million people working full-time from home.77 Furthermore, the question of whether substitution or complementarity is the more significant factor has been waged in the literature on teleworking for the past 30 years or more. Although there is disagreement: The preponderance of evidence suggests that when the scope of inquiry is broad enough, the net impact of ICT is to generate more communication, including new travel. Nevertheless, even if complementarity is accepted as the right answer qualitatively - and some people would contest that - we are not yet able to assess it quantitatively. Studies show part-time teleworking is more common than full-time, 1.5 days per week on average. Generally teleworkers record longer (substituted) commute journeys than the average national commute journey - in other words, teleworking is undertaken more by people with longer commute journeys. This suggests that the overall potential for reductions of vehicle miles travelled and pollutant emissions may be overstated (i.e. that people living closer to work will not telework to the same extent as those living further away, and this should be factored into any estimated aggregate effect). Looking at the range of studies that have been car