The American Society of Landscape Architects has put together a website with a lot of resources and references for transportation design. This is a nice complement to the more traditional engineering side of transportation planning and design, and underlines the value you can get from a well-functioning interdisciplinary design team even if it costs a bit more upfront. Here’s an excerpt from the street design page.

Bicycle lanes and sidewalks should be physically separated from vehicle traffic by trees, bollards, buffers, parked cars, or curbs wherever possible. Research has shown that physically-separated bike lanes yield the greatest safety gains for cyclists and, as a highly-visible piece of infrastructure, even have the potential to attract new cyclists. Vegetated buffers can further protect cyclists from harmful air pollution and should be incorporated whenever possible.

Green infrastructure should be widely used. Bioswales, rain gardens, and permeable pavement can be used to manage stormwater runoff and reduce flooding as well as create more aesthetically-pleasing streets. New construction should incorporate as many green streets features as possible, and existing infrastructure should be retrofitted to include green infrastructure. In Edmonston, Maryland, a 2/3 mile stretch of road was retrofitted with bioretention systems that now capture 90 percent of the first 1.33 inches of water on-site, helping to mitigate flooding and improve local water quality.