If you're planning to rent a car on a road trip in another country and think you will simply use your phone for step-by-step driving directions, think again.

Technology can be wonderful, but modern corporations aren't. They work against current advances by restricting your use of them. Waze and the mapping systems of major search engines work brilliantly at home. And they work brilliantly abroad, too—if you live there.

But your access is bound to be too slow. Even if you have international roaming turned on, your mobile phone carrier probably throttles the speed at which you're allowed to download data when you're in other countries. You may get data at much slower rates than locals.

Even people with robust international plans that grant unlimited data and unlimited texts usually find that those "unlimited" promises are hogtied by molasses-slow speeds. Your carrier probably doesn't trumpet the fact that its international speeds are drastically diminished, so be sure to ask what they will be. If they're super-fast, then problem solved.

In most cases, though, your phone's international data speed won't be able to keep up with driving directions. Your screen will be frozen in a constant state of loading—and you'll get lost.

The problem is compounded by the fact that precious few rental car companies give out printed maps anymore, and the maps that do exist are not very detailed. Renters simply assume customers will be using their phones because most customers do.

Here are some fixes:

1. Buy a supplemental plan that allows for proper high-speed data. These are costly, though, and they come with ceilings on the amount you're allowed to download (US$20 for 1 GB is common, and that goes fast). It's easy to breeze through your data allowance in hours, suddenly leaving you directionless and forced to pull over to pony up more cash for more data at a workable speed.

2. Bring an unlocked smartphone and buy a local SIM card that permits normal data speeds. This option is not for beginners, obviously, and outlets that sell SIM cards are dwindling as more standard mobile phone plans allow for international roaming.

3. Rent a car with a built-in GPS system. These models are always more expensive, but this is the easiest solution. The catch is that you should choose built-in GPS when you make your rental reservation, otherwise you may arrive at the renter to find there are no such cars in stock, or discover that you must upgrade—and you almost always get a better price if you book upgrades ahead of time online and not in person.

4. Reserve a hand-held GPS unit from the rental car location. Less expensive, which makes this the optimal selection. Sometimes the rental company will be out of units, though, forcing you to accept a higher rental rate for a car with a built-in system.

5. Bring your own hand-held GPS directional unit (not a phone) and plug it into the car. There may be data issues here, too—each system has its own way of working. And it's one more bulky item to pack. 

6. Bring a good map. I know—crazy, right?

Need some overseas road trip inspiration? Check out our favorite coastal drives in Europe.