11. The End of Traffic?

Figure 67: Understanding Dash's Traffic Data

What makes Dash's traffic data so different from all the other GPS devices is Dash's combination of data sources and intelligent logic to create a more detailed, accurate map of the traffic in your area.

Specifically, 3rd party traffic data provider Inrix supplies Dash with base traffic information in 106 metro areas in the United States. Dash Navigation supplements this data by compiling historical data models for all 106 metro areas, and preloaded that information onto each Dash Express device. On top of those two data sources, Dash incorporates the Dash Driver Network - information anonymously collected from other Dash drivers in your area.

The combination of historical, live, and predictive traffic patterns creates a level of traffic accuracy and completeness never before seen on a GPS.

Dotted lines on the map indicate traffic data that is either unverified or based on historical patterns. Solid lines indicate high-confidence traffic levels that are based on actual cars passing road sensors, or other Dash drivers who are on that stretch of road.

Also unique to Dash is traffic data for highway entrance/exit ramps, and surface streets. Currently no other GPS provides traffic data at this level.

Dash Express then incorporates all this traffic data in your projected ETA, and can more accurately estimate the arrival time.

Figure 45: Traffic Ahead

Should traffic conditions change along the proposed route, an alert will appear, notifying you that a traffic situation exists along your current route, and a male voice will verbally announce the problem (all other voice prompts are announced in a female voice). The estimated time of the delay is also displayed. Tapping "routes" displays alternate routes to avoid the traffic, or you can tap "close" to ignore the alert and continue along the current route.

Unfortunately, there's no way to tap on a red segment of traffic along the route and specifically exclude that area. The lack of more granular avoidances limited the value of Dash Express's excellent traffic information; without an easy way to route around traffic, it can be frustrating to see traffic up ahead and have few or no options to avoid it.

There were plenty of occasions when driving with Dash that I could see solid red traffic approaching, and the GPS offered no alternative routes. I would have liked to see a graphical detour function that lets drivers choose start and end point, as well as an easy way to avoid high-confidence traffic problems ahead.

12. Routing Engine Performance

All the bells and whistles aside, what really matters on any GPS is the quality of the maps, and how well the GPS figures out how to get from point A to B.

The single most common complaint I hear about any given GPS is "the GPS took me on a crazy route that I would never have chosen", and "that definitely was not the best/shortest way."

Arguably the most critical components of any turn-by-turn GPS navigation system are the routing engine and map accuracy. The routing engine is the software on a GPS that decides which route the unit should choose to get from point A to point B. Many people falsely assume that simply having the same maps on two GPS devices will result in the same routing choices. Not so, as there is a great deal of math and decision-making involved when calculating the "best" route.

Not surprisingly, this also one of the most difficult and complex aspects for GPS manufacturers to get right, and is the part of GPS navigation that is least well understood by consumers. Nevertheless, routing engine quality should be at the top of any GPS buyer's checklist.

The two largest mapping data providers are NAVTEQ and Tele Atlas . NAVTEQ used to have the advantage in mapping quality in North America, however in recent years Tele Atlas has improved its US database and both companies are now roughly equal in quality.

But there's a lot more to a routing engine than just the mapping data provider. How a given GPS will determine the "best" route is the result of not only the mapping data, but also how many additional data points, or attributes, are factored into the equation. For example, does the GPS know if certain roads closed after hours or on the weekend? What is the average rate of speed for a given road at a particular time of day? Statistically speaking, more accidents happen when making left turns as opposed to right turns -- is the GPS unit factoring that into the route? Each company takes all this data and compiles it in different ways, making unique decisions about what data is more important than others. The number of attributes used varies depending on how much money the manufacturer is willing to spend on their mapping data. For example, a full NAVTEQ map database that includes all available attributes can cost the manufacturer twice as much as a basic set of attributes.

Dash uses Tele Atlas maps, as does TomTom and several other GPS brands. Magellan and Garmin GPS units use NAVTEQ mapping data.

To test Dash Express's routing engine, I spent over 600 miles in the car with Dash Express, comparing the routing results to those of my trusty Garmin, Magellan, and TomTom GPS units.

To demonstrate the results, shown below are the routing results for two trips of varying distance:

Dash chooses a route similar to Google Maps up until the last mile, then appears to choose a slightly more efficient path, shaving 9 minutes off Google's estimated drive time.

Garmin's nuvi 660 chooses a slightly more efficient route out of New York City than Dash's, and is the only one to display which side of the street the destination address is on. It's a close tie between Dash and Garmin, with Garmin winning slightly for the better exit out of the city and more detailed arrival information.

Dash Express chooses a route almost identical to Google Maps, and is very similar to Garmin's route. Only the Garmin shows which side of the street the destination will be on. Garmin also has more detailed instructions throughout the trip.

Dash Express has a strong routing engine, and I was consistently impressed with the routes Dash Express chose. While not quite as strong as Garmin's mature routing engine, Dash Express was generally better at choosing routes than TomTom's GPS devices, and on par or slightly better than Magellan's Maestro GPS units.