Navigational systems that guide drivers from Point A to Point B, either with a GPS device or a smartphone, are now considered essential by many car drivers. So why not bike riders?

In fact, it’s happening. Smartphones such as Apple’s iPhone and newer Android handsets such as the HTC Droid Incredible can dispense bicycle-friendly directions to help cyclists navigate dedicated bike trails and streets with bike lanes, while avoiding hills and dangerous streets.

Bicycle advocates were thrilled in March when Google Maps began offering a “By Bicycle” option on the desktop version in addition to directions for driving, transit and walking.

“It’s kind of like giving us equal play with those other modes of transportation,” said Andrew Casteel, executive director of the Bay Area Bicycle Coalition, who uses an iPhone clipped to his handlebars to help navigate San Francisco and other Bay Area spots.

Several weeks ago, Google began offering bicycle directions on Android smartphones – a quantum leap beyond having to look up directions on your PC and scribble them on a piece of paper before setting off on your trip.

Meanwhile, an iPhone app, OpenMaps, uses the extensive and nicely detailed open-source cartographic data from OpenStreetMap to deliver bike map directions to Apple’s smartphone. The app is produced by a Romanian software developer, IZE, that uses route-finding technology from Menlo Park-based CloudMade. It has been downloaded more than 80,000 times since it debuted in July 2009, and it is particularly popular in Germany, where OpenStreetMap has some of its best map coverage.

As a two-wheeled commuter – I regularly combine my bike with Caltrain and the Valley Transportation Authority to travel between San Jose and Palo Alto and points in between – I’ve been keen to test out these smartphone services and decide whether it’s time to throw away the paper map that has long been my bike-navigation bible.

The answer, in short, is not yet. While there is much to admire about the OpenMaps and Google Maps products – and they are certain to get better as they collect feedback from users – they are still not quite good enough to serve as an exclusive method of route-finding. You might think of them as a couple of teenage boys – well-meaning, enthusiastic and smart, but capable of stunningly bad decisions.

Google, at least, is honest about this. Call up bike directions on your Android phone and the first thing you read is, “Bicycling directions (beta): use caution.” This is sound advice. As I pedaled between Caltrain’s Lawrence station in Sunnyvale and the Mercury News office in North San Jose in recent weeks, both Google and the OpenMaps app sent me like a moth toward the flames through the busy and dangerous intersection of Central Expressway and De La Cruz Boulevard near the airport.

To a computer algorithm, Central Expressway makes sense as a bike route – it has designated bike lanes and is relatively straight. But it is not a pleasant cycling experience, and the cars roaring past at high speed a few feet away don’t make it feel very safe, either.

A Google spokeswoman said the company has already heard from local cyclists about the Central Expressway problem and is working to alter its algorithms. But none of the routes the smartphone systems came up with was as good as the pastiche of shortcuts through parking lots and over pedestrian bridges that my commuting partner between Palo Alto and San Jose has discovered through several years of exploration.

Selecting a bike route “is a lot more of a personal question than a driving route,” Casteel said. “You don’t care in your car about hills or the traffic you’ll experience unless it’s going to slow you down. But on your bike, you care whether you are exposed to traffic.”

Still, these smartphone navigation systems are valuable to cyclists, even in their current, imperfect states.

Bike navigation apps

For iPhone: OpenMaps offers both a free and a paid bike navigation app ($2.99) at the Apple App Store. The paid app includes more extensive tools such as batch downloads of map data to your mobile device. We used the free app on an iPhone 3G, with a paid navigation service (99 cents a month) from Menlo Park-based CloudMade. Google also hopes to bring bike navigation to the iPhone.

For Android phones (we used the HTC Droid Incredible): Requires the latest version of Google Maps, version 4.2 for Android, which can be downloaded for free in the Android Marketplace, and version 1.6 or newer of the Android operating system.