AT MANY BRIDGES and tunnels across the country, drivers avoid long delays at the toll booths with an unobtrusive device that fits on a car's dashboard and sends a radio signal that records their passage. They are billed later. It's a tradeoff between privacy and convenience: the toll-takers know more about you but you save time and money.
An optional national identity card could be used in a similar way, offering a similar kind of tradeoff: a little less anonymity for a lot more security. Anyone who had the card could be allowed to pass through airports or building security expeditiously, and anyone who opted out could be examined more closely.