This is a composite beanbag photo. It’s a beanbag photo because I set the camera on my beanbag (see here for explanation), which sat on the concrete ledge of an overpass. This allowed me to aim the camera precisely where I wanted and to keep it nice and stable even with an exposure time of one second. There was no way a tripod could have fit where I needed it to.
It’s a composite photo because I took a lot of shots from precisely the same spot (thanks to the beanbag). Then I chose the best freeway shot and used Photoshop to lay it on top of the best sunset shot. If you look very closely, you might be able to tell where the two shots merge, but you have to be pretty eagle-eyed.