I did the experiment. To show my family Chongming, I drove from my home at 5:00 PM and went to Chongming via the Shanghai Yangtze Bridge and Tunnel, and get back to home at 6:30 PM. It takes about one and half hour to make a round trip to Chongming.
What an amazing trip. I love the wide 3 lane tunnel that crosses the river, and the 10km bridge. It cost 100 RMB for round trip, but compared to the silly round Lujiazui tour bus, the trip is more recommended for people who want to experience the Mega side of the city. It is another Mega Project in China.