I agree with mattc, it is possible to ride safely on roads and as mattc also points out there are things which can be done to make them safer for cyclists and peds.
Despite ian's optimistic tone I still don't think we will see a rapid adoption of measures that are prejudicial to the interests of motorists but help cyclists and peds. Remember the Dutch only got their cycling infrastructure in the 60s because public opinion drove political will.
I probably shouldn't have to explain that I don't mean
every road. But the moment you're dumped on a main, busy road, it's game over as a far as practical cycling is concerned. I can cycle to the end of my hill. Then it's a narrow heavily parked road into town. Like all such roads, it throws you into conflict with motorists who can't get by. Unless you like having a car revving behind or having to get out of the way of oncoming cars, it's not fun. Then you get to town, which is clogged with traffic going elsewhere, have to find the hidden bike-racks that aren't anywhere useful. Etc.
And it's not just about
safe, it's about pleasant. It might be safe to get to from (a) to (b) by walking by the side of the motorway, but it won't be fun or pleasant.
The mistake is to think that cyclists can change any of this. They can't because generally they're non-existent and as an other group (one that really goes out of its way to dispel any sympathy), no one cares. If you want to know how effect cycling organizations are, read the Cycling UK vs. BC thread herein and despair.
It's almost like there aren't many, many people who ought to share the aims of cyclists. Pedestrians. People who have seen friends, loved ones, relatives killed and injured on the roads, people who actually want a liveable environment rather than a dormitory in a carpark. They're the ones who would have the numbers and attitude to make change that benefits us all. Sadly, I think a lot of cyclists don't want that, they like being an other, fighting it out on the roads, telling their war stories.
But anyway, because it is for cyclists and because of the reasons above, Sustrans is fated to be crap.