My problem is that actually the A505 & A1307 at the points you go from Babraham & Pampisford to Abington aren't that dangerous as long as you don't try to turn right into the first Pampisford turn off past Sunny farm. The real danger area is crossing the A1307 onto the back road into Linton as you've got to cross two streams of traffic in one go at all logical crossing points & there are lots of other distractions/low visibility at the nearly straight across crossing points. No one is pushing any agenda forwards to do anything about those.
The whole area is a bit of a mess really, even in a car. As you say, the problem is crossing the A1307, but I've been going through the area for about 10 months now and if you take your time there is normally a break big enough that you aren't taking any risks.
Going from Linton to Cambridge, I go along the back road past Hildersham and turn right onto the A1307 just by the petrol station. Even at peak times in the morning, I don't have to wait long to get a clear road, meaning I can get past the pinch point by the petrol station before any cars can reach me (it's a 40 limit, but most are still doing way over that...)
Going home, at the moment, I take the new cycle path and go round the back of the Abingtons, and then cross going straight into Hildersham, the visibility is good and with the slip road, you can get off the main road very quickly. I used to go through Babraham and join the A1307 at the dual carriageway part, again, fairly good visibility and you don't have to wait too long for clear road, but the roundabout is really quite fast, and not fun at all when tired!