I've completed the first phase of a mobile ATCS setup in my truck. I'm a ham radio operator and have had a VHF antenna to receive voice communications for years (I operate 144-148MHz, railroads are 160-162). I'm adverse to drilling through my vehicles so I've always used no-drill methods. On my Ford Edge, I had a mag-mount antenna on the roof. For my F-150, first I used a fender-mount with an existing bolt right above the front left tire. It worked reasonably well, but I wanted to improve both my range and pattern a bit. So I built an antenna rack, similar to a headache rack, to not only raise the antenna, but center it a bit more over the metal of the vehicle. It fairly substantially improved my reception. However, my truck is already really tall for some parking garages anyways so having another 30 inches of antenna wouldn't do well so I had to build it to fold over and point my antennas out over my bed.
But when I'm out railfanning, I like to use ATCS on lines where it's active. Previously, I used an SDR dongle stuck into the side USB port of my tablet with a little 900MHz handheld antenna sticking off it, or the SDR sitting on my dash. This isn't ideal either, so I added a high gain 900Mhz antenna (the one to the left in the second pic) to the rack too. To avoid the higher cable losses at 900Mhz, I only have about 4 inches of coax under the antenna, I zip-tied the SDR dongle right there and run a USB cable into the cab. I gave it its first real field test today and it performed well, I got a few extra control points either side of my location than I normally do.
Also, don't worry, I don't look at it while driving! The key advantage here is I don't have to completely pack up and setup again if I move locations, and I don't have to balance my tablet on my center console, and if I start it before I leave, it can already be gathering data as I approach my watching location.