RAY: This puzzler was sent to us by Joseph Martinez. Joseph writes,

"I was driving on an access road about to get on the freeway. There was a convertible up in front of me, with the top down. It was a beautiful day. There was a couple in the car who I could only imagine were husband and wife. The car was a small sports car with a standard transmission-- a Miata, or something like that."

TOM: Maybe it was a Fiat?

RAY: I don't think so. It was moving at the time.

Joseph continues, "We had about three stop lights to go until the on ramp to the freeway, and at every stop light the couple would turn to each other and have a conversation. When the light turned green the conversation would abruptly stop until they came to the next red light.

"The car was not excessively loud. There was no loud background noise, and they did not have the radio on."

Here's the puzzler. Why did they converse only at red lights?