Along my commute I have a section that is much like you describe. Here's how it works for me. The path emerges from a regional park near my home. I ride into the regional park and follow the path to a road. The path continues adjacent to the road but I choose to exit the path and join the roadway. Why? The path turns away from my path about a mile and half past the park. To rejoin the roadway at that point I would have to jump a grass median and curb, cross a traffic lane back to the other side of the road while not at an intersection. In that mile and half, all the cars that go by me no doudt wonder why I'm not over on that nice path next to the road. Well, I've got 13 more miles to cover and that path dosn't go there. So I choose not to use the path for that short distance. I feel I put myself in more danger by having to merge with the traffic at an unexpected place if I followed the trail as far as possible (no vehicle would expect a ped or bike to be crossing where the trail veers from my route).
I'm not trail adverse. I use trails for about 1/3 of my commute. But they are some of the best designed bicycle commuter trails in the country. How's that trail you pass. Do you have to share with other users like peds? Is built with transportation in mind or recreation? Is it at least 10 feet wide? Does it provide enough access points to allow the transportational cyclist to get on and off when they need to? Is it a integrated of the transportion arteries in the region or just kind dropped in where there was space?
Do you understand better why they might make the choices they do?
Scot