Adverse impacts from roads are damaging the health and well-being of urban communities, yet the message that tree planting significantly reduces the harm isn't getting through to many highway engineers.
Money drives the mindset, with a focus on reducing immediate costs at the expense of the subtler benefits. Historically, it has been difficult to monetarise much of the value that trees deliver, which is convenient for the accountants, offering them a platform for ignoring tomorrow's benefits in order to balance today's books.
For the highway middle managers, there is little incentive to interrogate the conventional wisdom that trees are bad for business - roots damage infrastructure, they cause accidents by restricting visibility and they kill people who drive into them! Myths they may be, but entrenched they are - just the perfect foil to stifle progress.
This highways culture of living in the past is throttling aspirations for a green future, but emerging research and experience is challenging that traditional perspective. Indeed, far from detracting from desirable highway objectives, trees significantly enhance the prospects of meeting them.
Trees near roads buffer exhaust pollution right at its source, with big benefits to health. Trees in streets reduce vehicle speeds and accident rates in residential areas. Attractive tree-lined routes encourage public transport, pedestrians and cycle use.
The current generation of highway engineers is presiding over local decisions to meet their own narrow objectives, to the detriment of the wider population. We have the technology to get more trees into our streets. The challenge is persuading highway engineers to look beyond the roads and begin to work for the communities they serve, not outdated mantras.
Jeremy Barrell is managing director of Barrell Tree Consultancy