Last night I found myself on the Boulevard do Arco here in Sobral with a camera and some extra time on my hands. Not having a tripod with me, I setup on a park bench and over the next 4 minutes took 14, 15 second to capture the light streaks from the passing traffic. I stacked the images in Photoshop, the result is a 3 1/2 minute exposure of traffic passing the Arch.
Camera: Nikon D60
Lens: Nikon AF-S Nikkor 18-55 mm 1:3.5-5.6G
Focal length: 18mm
Exposure time: 15 seconds
14 images stacked to combine light streaks