Friday, September 30, 2011

Evaluating urban planning initiatives to increase active transportation

Ottawa Sun: Laurier St. bike lane in Ottawa (ON), Canada
Urban planning and epidemiology need to become better friends. Rigorous epidemiological studies that assess the health impacts of urban planning interventions are desperately needed. These studies can more reliably tell us what works and what doesn’t, and therefore where best to put our hard-earned tax dollars. I’m not sure why they are lacking. Money? Time? I guess they are all good excuses. But in the grand scheme of things, I would settle for even just a simple before-after study – something that I think is more than feasible.

Ottawa recently implemented a segregated bike lane pilot project on Laurier Street, running from Bronson to Elgin Streets. The lanes are blocked off from traffic with concrete curbs, plastic poles, parked cars and planter boxes. New road markings (including those gross green boxes) and signs tell cyclists where they should be. Most on-street parking has been removed and some bylaws have even changed, such as no right turns on a red light, which protect cyclists from absent-minded motorists. The project is part of the City of Ottawa’s plan to become a greener and more sustainable city.

All of this is great news for cyclists (and environmentalists), even though it has received some grumblings from residents and merchants on Laurier Street who have lost parking spots as a result. Since the lanes were open on July 10, 2011, almost 117,000 people have used them (that is, passed a counter at Laurier and Metcalf). Wow, that sounds like a lot of people…but wait a sec…How many cyclists used Laurier before? Maybe the same number of people used Laurier last year from July 10th to September 28th, 2010. So this number really tells us nothing. We have no idea what the ‘success’ of the pilot project is defined as either. Is it a certain percentage increase in the number of users, fewer accidents, more commerce, increase in physical activity, etc.? The main points I am trying to make here are that the city could have at least placed a counter in the same location BEFORE they implemented the project, as well as determined significant outcomes a priori and communicated those to the public. I don’t think it would have been that much more costly.

 I’d like to highlight that this would be something that is needed in the very least. These types of designs that use counters to count the number of users before and after are not robust against bias and cannot capture all that we would really like to examine. Here are a few examples why: 
  • We can only count users and not individuals so likely we are double, triple counting, etc. Perhaps increase in usage is only by those people that already cycle on the road 
  • If counters are electronic, I'm not sure if they can discriminate between cyclists and people that shouldn't be using the lane (such as skateboarders, motorized scooters, etc.)
  • We cannot determine impact on the health outcomes of individuals living nearby, such as increased physical activity or decreased obesity
  • Increase/decrease of cycling on Laurier could actually be due to other factors that we have not accounted for or reflect only secular trends (not due to the new lane)
I have had a very hard time finding an urban planning intervention with the intent of increasing active transportation/physical activity, or decreasing obesity, that has been well conducted. There is also the added caveat of residents actually knowing about the change to their environment. For example, if they don’t know about a new bike lane, trail system, or park how can they use them?

A study by Evenson et al (2005) perhaps is a basic model to follow– with, of course, some upgrades (e.g. addition of a control group). They set out to determine if a new rail trail built in Durham North Carolina (US) significantly increased time spent in leisure activity, moderate and vigorous physical activity, and active transportation of residents living nearby. 

Participants 18 years or older living within 2 miles of the trail were randomly recruited to participate in two telephone surveys conducted before and after introduction of the trail (n = 366). Questions were largely based on the Centers for Disease Control and Prevention’s Behavioural Risk Factor Surveillance System.  The researchers did not find that the new trail had any effect on the outcomes they looked at. There were some issues with the study which may explain why they did not find anything. Some examples include: 
  • The after measurement occurred just 2 months after the trail opened – this may not have been a sufficient amount of time (e.g. residents may still not have known about it). In fact, 38% of respondents said they weren’t aware of the trail [Correction - this should be 11.3%, 38 was the n]
  • The after measurements occurred in November, whereas the before measurements occurred in summer and early fall. In Canada at least, we tend to be outside less as the winter approaches versus in the summer
  • Low response and retention rates. The people who responded were likely not representative of the population (they already had high baseline rates of activity). What were the people who didn’t respond like? 

There are some other issues that I won’t get into but I think it’s a basic study that could easily be implemented by urban planners, with the help of public health professionals or universities with epidemiology or program evaluation departments (to increase the study’s robustness which is very important)! Who knows, maybe the City of Ottawa has done all of this and we just don't know about it - I'll give them the benefit of the doubt. Regardless, I truly think this is a worthwhile and necessary transdisciplinary endeavour that will benefit society as a whole. And don't get me wrong, I am for increasing biking infrastructure. I just want to make sure we can quantify its benefits and that we do it in the best possible way.

Evenson, K., Herring, A., & Huston, S. (2005). Evaluating change in physical activity with the building of a multi-use trail American Journal of Preventive Medicine, 28 (2), 177-185 DOI: 10.1016/j.amepre.2004.10.020

1 comment:

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