road tax

Sign this petition to lower the cost of road tax on motorbikes
http://epetitions.direct.gov.uk/petitions/48869

Normally I'd be right up for signing this kind of thing. But I'm not too sure about this one. Apparently the reason bike road tax is set at the level it is, is because there's no emissions tests for bikes. So they base the road tax on engine cc. Granted, we take up less room on the road, reduce congestion and don't rip up the road surface. But I have to ask, How will they judge road tax levels if this goes through? I'm pushing 1400cc with almost straight though race cans. I've got no idea what my emissions would be. But I've got a sneaky feeling if they start scrutinising that kind of thing I might be forced to put the bike back to standard if they clamp down on exhausts. And to be honest, It's my favourite mod on the bike!
It's also the case that bikes are seen as a luxury which we are all humped on anyway! I wonder what a new Scottish government would do if in power???