National Transport Studies
There are a few national reports examining the impacts of new roads and the actual traffic levels they generate compared with the forecasts made when applying for planning permission.
The A27 Feasibility Study is the latest study looking at the A27. However, as it is only really looking a the A27 and not at transport issues as a whole it is unlikely to resolve the many issues that people face moving around the area.
Local (A27) Studies
The most thorough local A27 study was the South Coast Multi-Modal Study published in 2002. However, even it predicted traffic growth far in excess of what has been seen locally (and nationally). Other more recent local transport studies have generally been commissioned locally by West Sussex County Council and include some economic assessments.