The traffic signal now flashing yellow for drivers on Rockville Pike outside the Bethesda National Naval Medical Center is scheduled to become active on Thursday afternoon. It’s part of the program to accommodate the new employees and patients arriving at the center as part of the federal base closings and relocations, known as BRAC.

The primary function of the new signal at North Wood Road will be to get as much traffic as possible into and out of the medical center during peak demand periods without seriously worsening the already heavy traffic on the six lanes of Rockville Pike, a major commuter route.

The Maryland State Highway Administration, which is working with Montgomery County and U.S. military officials on traffic controls and road improvements, will monitor the results.

The uncertainty over exactly how well the new signal will function reflects the overall uncertainty among planners about just what will happen as Bethesda’s roads, sidewalks, transit centers and neighborhoods attempt to absorb the influx of military patients and employees.

At a meeting in Bethesda Tuesday night of government officials and civic groups that have been working for several years to solve their mutual concerns about the changes, state highway officials described their hopes about advancing the reconstruction of intersections in the area. But at the same time, they warned that some funding remains uncertain.

All the parties are putting great hope in a new federal allocation of $300 million in transportation funds available to military hospitals affected by the national base realignments, but applications still must be filed to get some of that money.

The highway administration plans to rebuild the intersections at Rockville Pike and Cedar Lane, Rockville Pike and Jones Bridge Road, Connecticut Avenue and Jones Bridge Road and Old Georgetown Road at Cedar Lane. The projects would add capacity and improve traffic flow. But the program’s schedule stretches into 2015, and the construction itself is likely to disrupt traffic after the new staffers and patients have been added.

The transportation program for Bethesda also includes construction of a shallow tunnel under the pike to link the medical center and the Metrorail and bus station. But construction is not yet funded and, as with the intersection improvements, the construction itself will be a challenge for traffic managers.

Today, drivers on Rockville Pike see warning signs about the new traffic signal at the medical center’s North Wood gate. Once it’s fully operational, the signal will periodically stop northbound traffic for 50 seconds between 5:30 and 7:30 a.m. so that southbound traffic can turn into the medical center. From 2 to 4:30 p.m., the signal will stop the pike traffic for about 46 seconds to allow traffic out of the center. The red light cycle will be shorter after 4:30 p.m., because that’s when pike traffic will be peaking.

The state monitors will be testing the effects of this, but it will be a while before they have a clear measure of the impact. It always takes time for drivers to adjust to a new signal. In fact, that’s why it’s been set to flashing yellow for now. Traffic engineers routinely do that with a new signal just so drivers will start to notice it.

But in this case, traffic around the signal won’t settle down for a long time. The big influx of patients transferring from Walter Reed Army Medical Center is scheduled for the latter part of August. Around that time, students will return to school. In September, the summer vacation lull will be over, creating another traffic surge.

Engineers need to see the effect of the signal not only at that North Wood gate intersection, but also up and down the pike corridor.

They can adjust the signal timing, but would do so only after considering its impact on many intersections. “Everything has to be working together as a network,” said Edgar Gonzalez, Montgomery County’s deputy director for transportation policy.

Gonzalez did have a bit of good news to deliver. As part of the program to handle the new traffic impacts, the county and the community decided to completely shut down the Cedar Lane bridge over Rock Creek for reconstruction rather than keep it partially open. The idea was to speed up the work. In fact, it looks like the reconstruction will beat the accelerated target date of Aug. 26. Gonzalez said he now expects the bridge to be reopened by Aug. 5.