I'm wondering about what kinds of plants would be good to grow by busy streets. Specifically I'm interested in recommendations of climbing plants that could scale a wide column with or without a trellis. I'm thinking of doing a project that could use different plants for different climates. Initially I was thinking hops would be an interesting plant to do this with but I would be worried about using the flowers for beer or even composting them. What kinds of flowering, climbing plants would do at least okay in an environment that is close to auto traffic on a regular basis? Edit: specified flowering plants
The two I have in mind can be quite invasive, so I'd think carefully first before planting them, depending on where you live.
Trumpet Vine (Campsis radicans). Beautiful orange/red flowers, will climb anything, and can definitely handle the stress of living near a street as long as there is a bit of sun. In fact, in an older neighborhood I used to live in, these covered every utility pole on my block. They would grow tall enough to start growing along the wires, the utility would come and hack them to the ground, and in a few years they would be back up to the wires again.
Wisteria. Gorgeous lilac colored flowers, incredibly hardy, and will also climb anything. They do well with neglect, so again would be good for a project like the one you mention. Once they are mature, though, they have been known to take down the structure that was meant to hold them up if it wasn't built sturdy enough. I'm in the far northern part of the US where we don't generally see vines taking over houses, but I have seen a wisteria grow completely over a roof here. The same vine also seems to harbor an entire flock of house sparrows, which may or may not be the sort of habitat you're hoping to set up.
You can use hops, but maybe male plants, so that they will not produce the "hop".
In any case, I don't think this will be a danger for health, because hop is a very very small part of beer, and BTW I don't think the flowers accumulate heavy metals. Additionally, one should not use hop from "mixed" plants: seeds give a bad taste, so usually hops are cultivated with only female plants, far for any male plants.
Any plant (in high traffic) could cause problem on composting leaves, just don't use compost them for vegetable garden: some vegetables concentrate the heavy metals, which is bad in high concentration (but we need some of such metals in low concentration).
So I would use hops. Passiflora is also a nice and strong climbing plant, as jasmine.