Why? All three route you on I-66, the eastbound lanes of which are restricted to HOV-2 traffic in the morning.
My car’s navigation system gets around this problem by ignoring I-66 for most routings.
According to NAVTEQ, the company that provides map information used by the online providers and Acura:
“The NAVTEQ map data we supply quarterly to our navigation system vendors represents the direction of travel changes in the I-66 High Occupancy Vehicle (HOV) lanes to accommodate the morning and evening commute. While the timed carpool coding in the map data is coded to reflect reality, it appears that some navigation systems avoid these roads altogether, thus causing non-optimized routing.” (I give NAVTEQ kudos for providing a detailed response to my question.)
Another road in the DC area, the Rock Creek Parkway, is ignored by the big three online sites. The road runs in one direction during the morning and another in the evening and is two way the rest of the time. On weekends, the online routing turns a pleasant drive through the park into a convoluted route through many traffic lights and DC’s confusing traffic circles.
Because none of the systems factor time of day into the routings, you end up with illegal or suboptimal routes.
Ideally, the online providers would include time of day in calculating routing. In addition to HOV and other restrictions, they could utilize historical traffic data to provide more optimal routes during rush hour. e.g. avoid the Capital Beltway at all costs.
At a minimum, the online providers should put specific, prominent cautions on routes that use (or avoid) time-restricted roads and offer the user the ability to request routes that avoid (or use) these roads.