GPS vs. Real-Life Experience: Do Navigation Apps Really Know the Fastest Route?

There’s no doubt about it: modern Global Positioning System (GPS) accuracy has improved by leaps and bounds since the days of Transit, the first global satellite navigation system developed in the early days of the Space Program. Modern GPS can pinpoint the receiver’s position in your car or phone to within a few feet—or even better—and navigation systems like Google Maps, Apple Maps and WAZE use GPS data to help drivers find the fastest route to their destination in all sorts of traffic conditions.

GPS accuracy is undeniable as far as positioning is concerned, but how accurate are the apps that use it to plan routes and estimate driving time? I’m an old-school driver who likes to rely on instinct and intuition, but my friend won’t go anywhere without punching the destination into her phone and turning on the navigation voice. In both our experiences, the estimated and actual arrival times are seldom more than a couple of minutes apart, but we don’t always agree on whether the suggested route is the fastest one.

Let’s explore that.

How GPS Chooses Routes

Actually, it’s the navigation app you use that chooses routes, but before it can do that, it needs to pinpoint your location via GPS. The global GPS system consists of 30+ satellites, each equipped with a signal transmitter and receiver and a super-accurate atomic clock. The clock times how long it takes for the signal it emits, which moves at light speed, to travel to your device and back again. It takes into account the movement of the satellite (which is very fast by terrestrial standards—roughly 7,000 mph) by correcting for the Doppler Effect and even relativistic time dilation. For accurate placement, your device must communicate with at least four of these satellites at once.

Once your device knows your position, the navigation software takes over and places you on a grid. It establishes nodes and edges to the grid, and when you choose a destination, it uses algorithms to plan your route. It’s all about “weight” (the time it takes to travel between nodes) when it comes to establishing the fastest route, and here are some of the factors that go into calculating it:

• Historical data: In the absence of adverse conditions, navigation apps know how long it usually takes cars to travel a certain roadway at a particular time of day, and they assign that roadway a default weight.
• Road characteristics: Traffic lights, left turns, single-lane roadways, and stop signs along a route create penalties that increase the weight.
• Road conditions: The algorithm penalizes routes with poor conditions, such as heavy ice or snow.
• Crowdsourced pings: Navigation apps receive real-time data from other drivers, and when many cars are stopped or moving slowly along a route, the weight of that route spikes.

When GPS Is Most Accurate

GPS most accurately fixes your position when you are in an unobstructed area, and the weather is clear. Clear weather also improves the navigation software’s ability to calculate your driving time. When choosing the fastest route, GPS accuracy is best when traffic patterns are typical for that time of day.

When GPS Might Not Be the Best Option

GPS accuracy suffers in bad weather or when conditions aren’t typical. “Navigation apps can cut time in regular traffic,” says Chad Watwood, a lawyer who handles injury cases involving motorcycles, “but they are less accurate around construction sites, in rural areas, extreme weather or shortly after a crash. Haulers could also come across unexpected barriers when redirected onto new roads.”

GPS is ineffective if you can’t get a good signal because of surrounding obstructions, like mountains, and it also doesn’t work if your destination isn’t clearly defined on the navigation grid. For example, my house is in a rural, poorly mapped, mountainous area, and when visitors try to use GPS to find it, they often get directed to a road on the ridge opposite ours. For this reason, we always send visitors, workers and delivery drivers clear written directions and advise them to follow those rather than using GPS.

Pros and Cons of Following GPS Every Time

Have you ever gotten lost in a busy neighborhood? Perhaps you’ve gotten stuck in a traffic jam that you could have avoided by going a different way. GPS helps you avoid such situations and provides these benefits:

• Less stress;
• Improved safety;
• Reduced travel time;
• Greater likelihood that you’ll arrive when you say you will.

On the other hand, over-reliance on GPS can be detrimental. “Dependence on GPS alone may prioritize arrival times over road conditions,” says Watwood. It may also atrophy your innate sense of direction and make it harder to navigate on your own. Other drawbacks include:

• Distracted and unsafe driving;
• Misdirection because of inaccuracies in the software;
• Potential privacy violations because your movements are being tracked.

Smartest Strategy for Drivers

GPS-powered navigation apps can’t predict the future any better than you can. If you know by experience that problems are likely to develop along the route the apps suggests at the time of day you’re traveling, trust your intuition and choose a different route. As Watwood puts it: “Treat GPS as advisory: check routes, keep an ear out for audio cues and be willing to overrule the device.”

If you already know which way you want to go, and you’re familiar with the route, it’s a good idea to turn off the app, especially if you’re on a freeway. It may choose a different route and instruct you to turn at a place you aren’t expecting, which could create confusion and cause you to swerve into an adjacent lane. I’m speaking from experience.

FAQ

Should I always follow the GPS exactly?

Once you’ve decided to trust it, then yes. Second-guessing the algorithm only creates confusion and will probably cost you time.

Which GPS apps are best for finding the fastest route?

For several years, WAZE was generally considered the best because of its community-oriented crowdsourcing feature that lets users report accidents and other incidents in real time. More recently, Google and Apple have included similar features in their navigation software, and PC Magazine now rates Google the best, with Apple second and WAZE third.

About the Expert

• Charles (Chad) Watwood III is a lawyer handling motorcycle accident cases.He practices with the Georgia law firm LawBike Motorcycle Injury Lawyers.

Sources

• Aerospace.org: A Brief History of GPS; (2020)
• NASA: How Does GPS Work?; (2026)
• GPS World: Inside the box: GPS and relativity (2023)
• PCMag: The Best Navigation Apps for 2026 (2026)

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