The most efficient antennas are the monster 102 inch whips; that said, much more modest whips can be quite good without all that length hanging up in the air.
You might try some of the trucker newsgroups and see what folks are running. I was very surprised a few years back when I was working rotating 12 hour shifts and wanted some amusement during lunch on the night shift. I had taken my HT (hand-held) amateur radio 440 MHz transceiver with me to work and chatted with a number of *truckers* in Toranto. It seems a number of truckers are now using *both* cb and amateur radio. I am located in Rochester, NY and simply hit the Rice Lake repeater in Canada. My antenna was a 14 inch whip (equivalent to a 204 inch whip on cb) and my power was supplied by six aa alkaline batteries. One uses the repeaters to get the high antennas and more power for the distance. BTW, my HT has opened repeaters right from Rochester in Canada, New York, and Pennsylvania. All on battery power. I chatted with one guy through a repeater likely 60 miles away from me.
If you are traveling some distance, simply checking which repeaters are along your route will give you a *lot* of distance (our typical repeaters in Rochester will reach a mobile from Syracuse to Buffalo - figure close to 50 miles in any direction using a mobil radio at perhaps 30 watts or more - with a modest antenna. This is available almost any time. No interference during the day. They are also capable of Internet access whereby you can connect to any other repeater in the world connected to the Internet. You simply press the proper codes into the keypad and get connected. Some also have local telephone access. Heck, my HT fired up one day and I heard a friend calling me. He needed me in our Yahoo group. He called me on my handheld from Nazko, British Columbia, Canada (West coast). He used his computer to access the repeater that I monitor locally.
If it would have done your heart a wee bit of good to hear me using only radio - no Internet - chatting with Australia one day .... :)) That was through a linked repeater which took my 440 MHz signal and relayed it to another local repeater which transmitted the signal on 30 MHz (ten meters). The other repeater picked up the Australian on 10 meters and relayed it to my walkie-talkie on 440 MHz. I was running 1.5 watts.
It does give you the best of both worlds - local road conditions via cb and long distance via ham. 2 meter rigs are very popular. I like 440 as the antenna is quite small and we have a ton of those repeaters locally.
Check the truckers in the newsgroups and find out.
Best regards,
Jim