Update: more here at Mark Blacknell's blog
Investigation revealed that an adult man was riding his bicycle south on South Walter Reed Drive and turned right onto the access road of Four Mile Run Drive. It appears that when he turned onto Four Mile Run Drive, he crossed into oncoming traffic and struck an occupied vehicle.
This explanation makes sense in light of the markings on the road (I visited the scene after I heard the first ARLnow report, in the hope that I could better understand, first hand, what happened). However, it’s not clear to me, as cyclist who has made this same turn, why the cyclist would have taken that path.
Not sure if the cyclist was on the road or on the W&OD Trail. Here's Arlnow
A bicyclist has been struck and killed by a car at the intersection of Four Mile Run Drive and S. Walter Reed Drive this afternoon.
The driver remained at the scene and is cooperating with investigators, according to Arlington County police spokeswoman Det. Crystal Nosal. Police are still investigating the accident and expect to release the victim’s identification later tonight