(Inside Science) -- Science fiction writer Arthur C. Clarke once wrote that "any sufficiently advanced technology is indistinguishable from magic." For many people navigation systems either in the car or in smartphones are magical -- except when they aren't.
A series of strong storms that lashed the Northern California coast in February apparently exposed a rare but dangerous problems when technology, especially navigation technology, fails to provide drivers with accurate information about road closings, accidents and detours.
These problems became a crisis when a roaring atmospheric river from Hawaii, dubbed the Pineapple Express, hit the California coast near Monterey Bay and the beach town of Santa Cruz, home of a University of California campus, on the northern end of the bay.
The town sits on the plain between the ocean and the Santa Cruz Mountains. It connects to San Francisco to the north by the Pacific Coast Highway (PCH), which hugs the shoreline cliffs, and Highway 17, a four-lane highway that winds through the Santa Cruz Mountains to San Jose and Silicon Valley. The highway is used by an increasing number of commuters.
Moving north from Santa Cruz, Highway 17 climbs through a forest of second-growth redwoods to the Patchen Pass summit at 1,808 feet, and down into Los Gatos on the other side. Even in clear, dry weather, the serpentine road is perilous and subject to rock slides. During storms, fallen trees and mudslides commonly block it. Some commuters carry buzz saws in their car just in case they need to clear a downed tree from the road.
The storms that ran through the region last week caused road closures on 17 and other highways leaving few alternative routes for commuters. Many were left stuck at home or trapped at work. Those who did brave the roads found that the navigation systems or apps they relied on were woefully inaccurate. For days during the storms, Waze, Google Maps and Apple Maps provided inaccurate drive times. Some told drivers they could get over the mountain in the normal hour or so and failed to report blocked roads or advise drivers of needed detours.
"I'm a huge fan of Waze -- or should I say was," wrote Stephen Dix, a marketing executive in Scotts Valley, just east of Santa Cruz, via email. "It totally failed over the past 3 weeks in the Santa Cruz Mountain area. … Given how Waze is supposed to work I was very surprised."
Waze sent one user on a road covered with two feet of water. At one time, there were eight accidents reported simultaneously on 17, but the closures did not make the navigation systems.
"Fellow [H]ighway 17 warriors" wrote Richard Hugi, of Soquel on Facebook. "Please don't trust [G]oogle, Waze or the other apps, they are robots and will lead you down..er...up the wrong path."
Many said California Department of Transportation bulletins and Facebook were the only reliable sources of current information. All the main smartphone and standalone GPS systems, which report traffic, closures and accidents, may have been affected but Waze took most of the heat on commuter forums.
Navigation systems rely on a series of 24 satellites stationed above the Earth with three always in sight from any place on the planet. The system in the car or in the smartphones can spot its exact location within several feet by triangulating at least three.
The system is one of the best-known examples of Einstein's theories of relativity. Because of the clock differences between moving satellites and the relatively slower car, the system has to account for a 38-microsecond discrepancy to achieve its accuracy.
Smartphone navigation systems, like Waze, rely on crowd sourcing, or participatory sensing, to catch traffic, according to Katia Obraczka, a professor of computer engineering at the University of California, Santa Cruz.
Everyone using an application is reporting to a server as the car travels.
"As you drive, the information tells you where you are and it updates the map as you go," she said.
The systems typically monitor the average speed of cars on a route, supplemented with user-sent messages about blockages, accidents and police presence. Editors constantly update the maps.
(Google and Apple did not respond to requests for interviews. Waze, which did, is owned by Google.)
"Given the crowd-sourced, real-time nature of Waze's traffic application, we have the ability to actively monitor serious weather situations happening throughout the global Waze community," said Orit Yahezkel, head of localization at Waze via email.
"Wazers [Waze users] can report areas where there are road closures, and our community of map editors verifies the information being received, ensuring it is reflected accurately within the maps themselves so that road closures are up-to-date in real-time, shelter pins are dropped on maps in affected areas, and emergency response information is readily available for anyone stuck in bad weather."
But if cell phone service is spotty, as it is in the mountains, or jammed, as it is in a crisis, that information is never passed on to the navigation application server and hours can go by without the problem being registered, Obraczka said. That's apparently what happened in the storms.
She knows how unreliable the apps can be. Several weeks before the storm there was police activity on Highway 17 and Waze didn't warn her until she got to the highway. Then it sent her, and everyone else who relied on a navigation system, down a two-lane road to the valley below.
The resulting traffic "was pretty nasty," Obraczka said.