In Japan, ETC has become widespread.
It was said that Japanese system has a problem.
On-board equipments were very expensive,
because it needed two-way active communication on 5.8GHz
DSRC (Dedicated Short Range Communication).
But now on-board equipments become affordable.
a cost per vehicle starts from 100US.
And some incentive campaign has been done.
So I bought one for my micra, Denso's DIU-3500.
Previously, I bought ETC for my father's car, which was also Denso's DIU-3200.
It's antena was bigger than micra's because its antena was designed to set on the dash.
DIS-3500's antena designed to attach on the windscreen.
It looks smart!