High gas prices and a slowly improving economy have revved up Indiana mo-ped sales, according to dealers in the state.

Mo-ped sales at Indianapolis-based Midwest Scooters have doubled within the past six months, said Steve Schafer, the store's general manager.

Mo-peds — defined by Indiana law as scooters with engines no larger than 50cc and that travel no faster than 25 mph — do not have to be registered with the Bureau of Motor Vehicles. Anyone 15 or older with a driver's license or state-issued identification card may operate one. Insurance is not required.

The unregistered vehicles are commonly associated with riders who had lost their driving privileges because of drunken driving arrests, Schafer said. But higher gas prices have made the vehicles — which cost anywhere from $600 to $3,000 — more popular as a cost-effective means of transportation for both adults and teens.

Schafer anticipates sales will pick up even more during the next few weeks as high school students start their summer vacations.

A mo-ped regulation bill died early in conference committee at the Indiana General Assembly session.

The number of mo-peds in Indiana is unknown, largely because they are not required to be registered, according to a March report by the state's Legislative Services Agency.

If mo-peds were more tightly regulated, Indiana could generate revenue from registration, license and identification card fees.

Last year, the state generated $5.5 million after the Bureau of Motor Vehicles completed more than 212,000 motorcycle registration transactions.

A Lafayette businessman said mo-ped sales are so good, he is installing sound systems on them.

Travis Kearney of Lafayette recently started installing MP3-compatible speakers in glove boxes in the motorized bikes.

The speakers can connect to amplify any device with a headphone jack, including smartphones, iPods and MP3 players, which also fit in the glove box.

Kearney, 34, said he started the service after noticing that today's riders and passengers now want more amenities — especially music — on their mo-peds.

The part-time medical interpreter said his service has generated a steady flow of orders.

Kearney said with speakers, riders aren't wearing headphones and fiddling with MP3 players while moving.

Wearing headphones while operating a mo-ped is not illegal in Indiana, but Indiana State Police Sgt. David Murray said it can be a distraction to drivers.

"Any distraction — regardless of the source — that takes away from your attention to the road is dangerous," Murray said.

Natasha Davis of Lafayette originally purchased a mo-ped for her 16-year-old daughter so she could cruise around town with her friends.

In April, Davis hired Kearney to install the speakers because her daughter wanted to listen to music while she drove.

She said the service — which starts at $150 for a basic installation — was worth the money.

"It looks great," Davis said. "She doesn't want to get off of it now, so I think she loves it."