You could look at the elevated garden city as a super cheap way to get an underground set of roads and car parks. Rather than having multi-storeyed car parks you could have the bottom floor of most buildings as car parks. Think how much energy and time is wasted going up and down multi-level car parking buildings.
For shops rather than having one or two car parks outside you could have 10-20 directly under the shop for your customers making it super easy to have access.
Think how cheap it would be to have a ground floor bus exchanges of real scale and usefulness.
It could be possible to future proof the design with space for light rail network on the ground level.