The Rock Creek Park website has a document available online from 1985 called "Rock Creek Park - Adminstrative History". There's a section on bicycling and it's really quite interesting. It shows that while much has changed, in some regards, things have stayed the same.
The 1960s saw a resurgence in the popularity of the bicycle as a mode of transportation and recreation for adults as well as children. Rock Creek Park made its first special effort to accommodate cyclists early in that decade, when Ross Drive was occasionally reserved for their use. In 1966 the section of Beach Drive from Joyce Road to Broad Branch Road was first limited to bicycle and pedestrian traffic on Sunday mornings. By that fall about three and a half miles of trail north of the Nature Center had been bluestone-surfaced for bicycle use. In the following years the Beach Drive automobile closure was extended to Morrow Drive, and the bicycle trail was extended.
These initial efforts were not altogether successful. The trail was overly steep in places, and the surface was not stable enough for thin tires. Bicycle use on the closed roads did not appear sufficient to justify their closure, and motorists complained. They also objected to sharing roads simultaneously with cyclists, who tended to hold up traffic.
Thank goodness those days are over. And here's how the trail got paved.
In September 1971 [cyclists] prevailed upon the Park Service to set aside one lane of the Rock Creek and Potomac Parkway north of Virginia Avenue for a week to promote commuting by bicycle in lieu of automobiles. The experiment was well publicized and enjoyed a good response from cyclists, but its positive aspects were overshadowed by massive traffic tieups with severe inconvenience to the great majority of parkway users unable or unwilling to shift to bicycles. The political impossibility of continuing the lane closure--the goal of the bicycle lobby--was quickly apparent. The Service compromised by paving over the existing bridle trail between Connecticut and Virginia avenues for bicycle use; the crash project was completed by the following week.
In 1980 they studied nine alternatives for completing the bicycle system.
At one end of the spectrum, 5-1/2 miles of new bicycle trail paralleling Beach Drive would be built, entailing no effect on auto traffic. At the other end, major segments of Beach Drive would be permanently converted to bicycle use only, eliminating it as a through route for automobiles. Michael A. Replogle, an engineer with transportation experience, advanced a tenth alternative in March 1981 on behalf of the People's Alliance for Rock Creek Park (PARC), an outside group. His plan would permanently close Beach Drive to through auto traffic both above and below Joyce Road as soon as the Metro subway system was opened to the Van Ness station on Connecticut Avenue.
If you think the Klingle Road fight is ugly, just imagine how nuts people would have gone then. Still, that was probably a missed opportunity to make Rock Creek more Park-like. At first NPS leaned in that direction.
In March 1983 the Service advanced a three-phase solution largely endorsed by PARC. Portions of Beach Drive above Joyce Road would be closed to cars on weekends and holidays during the warm months. One lane of Beach Drive south to Broad Branch Road would be reserved for cyclists and joggers during weekday rush hours, allowing cars the other lane in the prevailing rush hour direction. After 1985, when the Red Line of Metro was to be completed beyond Van Ness and reconstruction work on 16th Street was to be finished, a gate would be placed near Boulder Bridge permanently barring that section of Beach Drive to automobiles.
Which is why things are that way today. What? They aren't?
Three months later, however, the Service disappointed the bicycle forces and others interested in curtailing auto traffic by a change of position. It confirmed the weekend closings on upper Beach Drive between Picnic Area 10 and Wise Road and between West Beach Drive and the Maryland line--measures previously tried with good results. But it would not interfere with weekday traffic below Joyce Road. Instead, it would build a 2.5-mile bicycle trail paralleling that segment of Beach Drive down to Broad Branch Road.
WABA and NCPA both opposed the decision and then it appears that they fought about the trail, which WABA supported and NCPA did not. Which is where they were in 1985.
Further measures to curb auto traffic in favor of bicycles do not appear imminent.
No, they don't.