Just use the geo-processing tool "Merge", and selecting the layer containing the buffer polygons as the input. A simpler way is to merge them when created, using the buffer tool.
thank you for this detailed response.
I have tried to run through your methodology but have ended up with slivers for example where the roads form bends. Also, when I dissolve the result of the first intersection operation, for some reason, not all the polygons in the junction areas are dissolved together. Again, this may be a function of the geometry, i.e. where junctions are not completely perpendicular, the polygons might not actually touch and thus not be 'recognised' as belonging together.
I think with a different dataset, your suggestions could work, though, so I will definetely keep them in mind for future reference. For my current project I have decided to approach the problem somewhat differently, as my dataset is too large to correct all 'errors' by hand.
I would say that looking at your original lines that you needed to first dissolve the roads into continuous lines, then perform the buffer. That would smooth out the bends without slivers. I also noticed the parallel lines for freeways and offramps. I would handle them in a separate process.
If you come up with something better for your data, share it. You are not the only person to face this kind of need with a road network.
Thanks for the reminder. As far as dissolving the original lines goes, my problem/task is to maintain the individual segments of even the same roads as I am using traffic loads on the network to calculate emission loads for each segment. And the traffic and thus the emissions vary on different segments of even the same road (the data comes from a travel demand model).
And my "work around" entails doing something completely different than my original plan as I came to the conclusion that I would not be able to solve the buffer/overlapping polygons problem. It has turned into a fairly lengthy process and I am not sure it would be much use to anyone unless they try to do more or less exactly what I am doing. I am happy to post it, though - just in case. By way of explanation: I am working with two network features. One is the centre line of the real world road network, the second is the simplified (and not always spatially coincident) network from a travel demand model, which contains the traffic loads for the road segments. I am interested in the emissions that are created within a certain distance of inhabited land parcels (i.e. ultimately the emission loads affecting people living in those parcels)
- selected links from real network that are within 300m of inhabited parcels: CandidateNetwork1
- selected all of these that are "intersecting" with model network with a search distance of 300m (this is to try and bring the data from the model network together with the real network in some way): CandidateNetwork2
- deleted all links from CandidateNetwork2, that do not have an equivalent in the model network from which traffic/emissions data could be transferred
- created 300m buffers around CandidateNetwork2
- clipped the layer of inhabited parcels by CandidateNetwork2 (getting all inhabited parcels or parts thereof that are within the buffer distance of the real network)
- buffered the parcels by 300m
- intersected the clipped parcel layer as well as the buffer layer with the model network (thereby getting as close as I saw possible to correctly assigning traffic/emission loads from the model network to parcels that in reality are within the chosen distance of the real network) - on this last step, I ran into big problems with the buffer polygon/network intersect step, though - described in another post in this forum
That's it for the work around (once I have worked out the intersect problem). Maybe it is of use to someone.