Given the shortcomings of vehicle batteries–their high cost, the time it takes to recharge them, and the fact that they store less energy as they age (they’re expected to lose about 20 percent over 8 years)–many researchers are looking for alternative ways to power electric cars.

Powering them from overhead lines, the way many city buses get power now, doesn’t seem practical. But some researchers are suggesting embedding wireless power transmitters into roads that could top off a battery as a car drives over them. This would make it practical to use smaller, cheaper batteries that could be replaced every few years.

Normally, such systems would require bolting a power receiver to the bottom of a car. Now researchers at Toyohashi University of Technology have demonstrated that power can be transferred from electrodes buried in a road to the steel belts inside tires. That power was used to propel a scale model of an electric vehicle (according to Green Car Congress). The researchers say the energy transfer is as efficient as charging and discharging a lithium ion battery.