FRANKFURT, Germany — Thousands of people are demonstrating in Frankfurt to demand more action against climate change as the German city’s auto show opens to the public, with some cycling into the city along highways that were temporarily closed for the occasion.

Demands raised by the organizers of Saturday’s protests include an end to the combustion engine, climate-neutral transport by 2035, a speed limit on the autobahn and a strong German climate policy package.

Environmental groups say the trend toward bigger and more powerful cars, particularly SUVs, is eating into the fuel efficiency gains of recent decades.

On Thursday, when the Frankfurt Motor Show officially opened, Greenpeace activists unfurled large banners branding the models on display “climate killers.”