The CB radio is a semi-mobile exchange communication system common onboard freight carrier (trucks for example) Wikipedia CBRadio.
It allows the driver to communicate information between each others while en route. This would basically gives the chance to a hitch-hiker to assess other potential ride before being dropped somewhere.
Its usage is mainly common with truck drivers within certain countries such as Poland, Canada and the United States but can also be common with 'outback' car drivers. It can also often be present at the truck stop or offices dealing with transport carrier or the 'outback' (such as Natural Reserves and National Park in North America).
In Poland truckdrivers commonly use CB Radio to help a hitchhiker find a new driver. On rest areas a driver may approach any hitchhiker to offer a search for a driver (on the main road) within the range of the CB radio message transmission area.