Electronic toll lanes may operate alongside conventional toll booths so that drivers who do not have transponders can pay at the booth. Open road tolling is an increasingly popular alternative which eliminates toll booths altogether; electronic readers mounted beside or over the road read the transponders as vehicles pass at highway speeds, eliminating traffic bottlenecks created by vehicles slowing down to go through a toll booth lane. Vehicles without transponders are either excluded or pay by plate – a license plate reader takes a picture of the license plate to identify the vehicle, and a bill may be mailed to the address where the car's license plate number is registered, or drivers may have a certain amount of time to pay online or by phone.