Imagine driving on a rural interstate at 70 mph. The speedometer suddenly drops, and the car's engine quits without warning. You call a roadside assistance plan and has to get the car towed more than 60 miles.

You could end up saving at least $50 in long-distance towing charges.

But if the coverage doesn't match your needs, you could be left stranded. How can you ensure the coverage is worth it?

"Understand exactly what is cover(ed) and how often you'll use it and what your return on your annual investment will be," said Tara Baukus Mello, senior writer and lead market analyst at NADAguides.com.

What's Offered?

Auto club plans largely offer towing, flat tire servicing, jump-start service, lockout assistance, trip planning and fuel when a vehicle runs out of gas. Some plans, such as AAA, AARP Motoring Plan and BP Motor Club also offer vehicle repair warranties.

"My best advice is to ask questions, especially if it's a lesser-known or newer service, so you know exactly what you're buying," Mello said.

Furthermore, drivers might want to consider the vehicle's condition and their amount of driving, particularly if it's long distance.

"It depends on the condition of your vehicle. It's certainly possible you have one of those roadside assistance plans for 20 years and you never use it," Mello said. "If you drive an older vehicle, then you certainly can end up getting your money's worth."

AAA has 51 million members in the U.S. and Canada. Beth Mosher, a representative of AAA Chicago, said AAA is the largest motor club and paid membership organization nationwide. Basic memberships start at about $60, but there may be an enrollment fee. Regional club services vary, but can include auto loans, insurance and prescription drug discounts.

Service For Bikes

The Better World Club not only dubs itself as the only eco-friendly auto group, but it is the first U.S. program to exclusively offer roadside assistance for bicycles, according to its Web site.

It offers help for cars, but will tow bikes up to twice a year and send out someone to help fix a flat tire, though it won't deliver new equipment.

GM Motor Club offers unlimited towing and unlimited service calls, even for drivers who don't own a GM car.

The Sam's Club roadside assistance service gives members a mechanic advice hot line and a DoubleCheck estimate on repairs by an objective technician, according to its Web site. It also offers rewards of up to $5,000 in hit-and-runs. Plans are only for Sam's Club members, however.

Automakers typically offer buyers roadside assistance when they purchase a new vehicle. Mello said these programs are often associated with midtier service.

"It's often a perk with the sale of a new vehicle, and it's often the first year or X number of miles," she said.

People also may be able to get help from their credit card or mobile phone companies. Before buying another plan, people should make sure they don't duplicate coverage, Consumer Reports said.

Other Factors

Mello said that people need to get the details straight before enrolling.

They should ask if other family members are covered, as well as check about RVs, motorcycles or other vehicles people might drive beside their own cars.

Also, people need to see if the plan is limited to certain states or regions.

Complaints About Service

Mello said that many times, members who complain are not dissatisfied with the roadside assistance program itself, but with the vendor dispatched. She said the programs should be made aware of any problems with its vendors.

She suggests contacting the program and the Better Business Bureau where the company is based. If it's an automaker's program, members can call the 800 number inside the vehicle owner's manual.

No matter what an auto club plan's bells and whistles include, reliability in a time of emergency can mean everything to members using a roadside assistance service.

"If you're looking at a $50 or $80 investment, you're also buying peace of mind and peace of mind means a lot to people," Mello said.