From the SPD Blotter:

"On 04/09/11 at 1:00 p.m., a 40-year-old grandfather and his 2-year-old grandson left in a vehicle, and were to return in two hours. When they didn’t return the family became concerned and called the grandfather’s cell phone. He did not return their calls.

At 3:19 a.m. (04/10/11) the family reported the child missing. The family believed that the grandfather may have relapsed (drugs/alcohol), and the child was possibly in danger.

The Officers handling the call entered the vehicle in WACIC with the missing child’s name, and entered the child as missing.

Late this evening, while conducting a search for the child and vehicle an officer was able to locate the vehicle using history he found in the LPR (license plate recognition) vehicle. He was also able to question people at the location of the car, and determine where the 2-year-old was (West Seattle). The grandmother was notified, she responded and recovered the child. Officers responded to the grandmother’s house to check the welfare of the child. He was in good unharmed and in good spirits."

The LPR vehicle used by police works like this, according to the SPD website found here:

The technology is License Plate Recognition and works much like a camera. It is installed on a Patrol Vehicle and automatically takes "digital" pictures of the license plates on the vehicles that the patrol car is passing. If the license plate that was read is listed as a stolen vehicle or is flagged for any other reason, the officer is notified that they have just passed a "vehicle of interest."