From the moment we leave home and go on our journey to the shops, work or school, we use roads and paths that were established as a result of historical demand for travel.
The more desired a route is, the more likely it is that it has been turned into a main road, and with increasing traffic, lanes have been added, junctions signalised and going along or across that road has become a highly regulated process.
Cars have to stop at signals to give way to other vehicles going in perpendicular direction, pedestrians press buttons and wait for a ‘green man’ to show. The more demand there is to use a given connection, the more capacity is added and in effect more people come to live and work in areas served by that road, thus inducing even more demand.
Cycling on a busy road
No matter which form of surface transport we use, be it walking, cycling, driving or taking a bus, we all share the road with others and the air on many of these roads is becoming more polluted.
Research from Australia and the US shows that cycling on the busiest roads can lead to higher inhalation of air pollutants in some instances. Although it is worth noting that the lung function results indicate that elevated pollutant exposure may not have acute negative effects on healthy cyclists.
The US study researchers conclude that by selecting low-traffic Bicycle Boulevards instead of heavily trafficked roads, cyclists can reduce their exposure to vehicle-related air pollution.
Similarly, the Australian study concluded that for bicycle commuting at peak times, the health risk may be substantially reduced by decreasing proximity to motorised traffic, which should be considered by both bicycle commuters and urban planners.
Health benefits outweigh exposure cost
Proximity to traffic is clearly a factor affecting one’s exposure to pollution, but how far from traffic do you need to be to see a beneficial health benefit?
One study says that the concentration of black carbon (by-product of the incomplete combustion of fuel that contains very fine carcinogenic particles that are especially harmful to health as they can move through and beyond the pulmonary system) decreases by 2.5% with every five meters in distance from the nearest traffic lane. The concentration of pollutants is especially high around junctions where drivers apply breaks and then rapidly accelerate.
Similarly, studies of air quality on low traffic routes indicate that pollution peaks appear where the route intersects with roads carrying large volumes of cars.
Cycle paths (understood as off-road infrastructure away from all traffic) on average have 12% fewer crossings with roads than on other types of routes. Nitrogen Dioxide (NO2) concentrations on city bike lanes compared to off-road bike paths, has been found to be over 30% higher, and cyclists in bus lanes risk exposure up to 60% higher than on off-road cycle paths.
Despite the above, it is important to note that the health benefits of cycling anywhere is the UK still outweigh exposure costs. The biggest study into the link of cycling and health shows that using two wheels can halve the risk of cancer and heart disease providing a clear evidence that people who commute in an active way stay healthier.
Off-road paths and Quietways: why they are great
This takes us to an obvious conclusion – cycling is good for you, and it’s even better when we have more convenient access to, and better connections between, all the infrastructure not used by heavy traffic that we may already have in our cities. Examples include canal paths and parkways that attract leisure cyclists. Whilst off-road cycle paths may not provide the most direct route, they offer a pleasant and enjoyable experience.’
Traditional transport modelling techniques typically encourage us to plan routes from A to B along the quickest path. This approach may overlook journeys which are not so time-sensitive and have additional motivations, such as relaxation or fitness.
Where would you prefer to cycle?
Research into cyclists’ route choice preferences shows that around half of all cyclists would change their route in order to travel through parks or green areas. That is especially true for novice cyclists and women. Clearly, if we want more people cycling, we need to support these underrepresented groups who may not have the confidence to cycle on main roads.
An interesting finding came from a survey that asked how much people are willing to extend their journeys just to cycle away from main traffic. It found that cycling on an off-road path is worth, on average, 3.17 minutes for every 1 minute spent with traffic. That’s over 300% preference. It gets more striking when looking only at females with reported 5.19 minutes and a massive 7.2 minutes for least regular cyclists.
The willingness to trade off time for cycling away from main roads could be explained in light of the increased perceived safety and convenience of these cycle paths.
With many journeys being less time-sensitive than commuting and knowing that even commuters are willing to extend their journeys (and are prepared to use a noticeably longer route) is an indication that there is a need for more sophisticated planning of cycling infrastructure and a greater mix of off-road and on road routes.
Mapping “fresher air” routes
At Sustrans we work closely with partners and communities so that people have access to a network of safe routes and better places to move around, live, work and play.
Generally speaking, it is much easier to implement improvements and increase accessibility of off-road infrastructure and add signage and markings to calm streets than is it to change main roads.
To test this in a real life scenario, I ran a network assignment model for commuter journeys in Newcastle-Upon-Tyne.
My model excluded all major roads (primary, secondary and tertiary roads) and any other links within 25 meters (i.e. segregated cycle path running in parallel right next to a main road). I also added a preference for traveling on cycleways and paths, with the least preferred option being cycling on residential streets.
Having all major roads removed from the network, there was no option for the model to route journeys even on the shortest bits of road carrying traffic of any significance, so all journeys were completely carried on off-road paths and calm streets. These route options present clear opportunities for increasing share of cycling in Newcastle’s modal split without disruptions to the city’s logistics during construction of segregated facilities and not exposing final users to pollution from heavy traffic going in the same corridors.
Implementation of these schemes would have narrower impacts, but they are more likely to be quickly delivered and bring immediate benefits to local communities.