Revel, more commonly known for its fleets of rental mopeds, plans to launch a ridehail service in New York City next month. Its effort is just the latest chapter of venture capital-backed transportation startups using legal gray areas or loopholes to add more vehicles to streets.US cities have grown accustomed to startups arriving with cars, buses, bikes or scooters and grand promises of improving transportation. Uber and Lyft spoke of ending car ownership and making cities better places to live.