A fanciful scene for a race poster by motoring artist Géo Ham- I don't think unmanned sidecars raced with solos! This was the first Grand Prix event held after the war, the course set up at St. Cloud in Paris for the event and never run again. This was a combination car and motorcycle event, Wikipedia has the car results. I was hoping to be able to put together the track route through the streets, and the view below looks like a reasonable location for the scene on the poster.