The idea is simple.
I think you can have bus routes from slum areas to cities, work and food places. The reason is that this would increase people living in slum areas better chances of livelihood.
Money can be ?saved since its cheaper to bring home food by bus. This money can then be invested in local business. Upgrading the slum.
Also it will better for the environment. I think you just need to make light-weight wheels on buses to have it running electric.