A bike-sharing craze that has swept China over the past two years is picking up speed in cities across the United States, but with a different spin as tough local regulations rein in the roll-out of dockless bikes.

Chinese startups pioneered dockless bike sharing: unlock a bike with your cellphone, ride it, park it, and relock it. But the downside has been bikes piled everywhere in many cities, clogging the sidewalks.

Many major U.S. cities have pre-empted that problem with rules that sharply limit how many dockless-bike companies can operate and how many bikes they can offer in an effort to avoid problems with blocked sidewalks.

Mobike, one of the Chinese bike-sharing giants, has launched in just five U.S. cities and is deliberately moving slowly to work with local communities, according to U.S. General Manager Jason Wong. In Dallas, a city that bike-share companies say is lax on regulation, Mobike has “voluntarily capped” its dockless bike number at 3,000 to make sure the business can thrive in the long term.

Ofo, another Chinese dockless bike-sharing power, will not enter a city without the blessing of local officials, said Chris Taylor, head of the company’s North America business. It is now in 25 U.S. cities, including Seattle, San Diego, and Washington, D.C.