Unfortunately the marketing department got control and the current Insight has grown into an almost straight copy of the Prius. It's a quite big 5 door compact that's too big, too heavy, has too much engine and the aeros have been compromised by the need to look "normal".
Honda's trick of building the electric motor into the flywheel and replacing the starter motor with it is genius as is combining it with auto-engine off. This could be applied to a modern diesel as well.
Meanwhile my trip down the M4 involved battling with BMWs, Mercs, SUVs and loads of other big old cars with big old engines and automatic boxes being driven badly at excessive speeds. It really shouldn't be hard to get 2 people in comfort to do 100mpg (imperial) at a real 75mph. All it takes is the willpower and the marketing to make that idea attractive.
