There was a discussion about the turnstiles in November on the Usenet group ne.transportation. Sean Sullivan said this:With this insight, I realized a common thread - the AFC gates failed to open when I was carrying shopping bags! Apparently when I’m putting a card through the AFC, the position of a dangling shopping bag is just right to interfere with the system.
So now I carefully stand behind the plane of the AFC gate’s front panel, put the card through, keep standing there while reaching over to collect my card. The gate has opened every time.I can’t vouch for his observations, as I rarely enter a turnstile with shopping bags, but he could be correct. I can only hope that the machines can be changed to make this clumsy procedure unnecessary.
The turnstiles may have sensors to prevent two people from slipping through on a single card swipe. The security gates in my ofice will react loudly to a briefcase or bag if it is too far ahead or behind the carrier when they pass through.