The site
Innovative Transportation Technologies for better urban livability and improved mobility has a compendium of proposals. There are some basic engineering principles that need to adressed. The material science aspect and the geometry both affect cost and reliability. Any structure that is exposed to the environment is affected by thermal expansion cycles, chemical corrosion, and various forms of radiation chiefly UV. What are the design flaws in you have identifired in highway construction. It is key to make these known so that they can be minimized in the near term since economic stimulus dollars are being poured into bridgeand highway repair. What is obvious to an engineer is easily ignored by lawyers in the legislatures. Even in my lifetime there have been improvements in concrete and steel technologies. My brother worked for NYSDOT doing quality inspection for concrete batches. I did QA inspection on some of the car interior panels of the Washigton Metro Area Transit Authority that had the fatal collision of two trains on the same track a few years ago. The new car protected the passengers while the old car did not. It is easy to be dismissive of other peoples' efforts.
The thickness of concrete and spacing of rebar generally have the greatest effect on strength and durability. My experience with permanent magnets is that there is some small but noticeable reduction in field strength with use. This would have to be taken into consideration over time and use.
I am looking at a Master's thesis of a Swedish grad student on incorporating velomobiles in urban planning. These may be part of the pallet system. Currently cars have four hard points to contact lifting equipments and hooks for towing that can be used for support rather than the roof.