A recommendation from the mayors of Rockville and Gaithersburg that developers study how a planned 4,360-acre medical and biotech research campus between the cities will affect traffic in their cities is reasonable and will help prevent already-clogged roads from becoming worse.

Mayor Phyllis Marcuccio last week told an advisory committee working on the proposed Great Seneca Science Corridor that traffic studies in Rockville are needed; Gaithersburg’s Sidney Katz agreed later in the week.

The project, expected to be completed in 20 to 30 years, in impressive 52,500 employees, 17.5 million square feet of commercial space and 9,000 residences. There’s no question it will significantly change commuting within the two cities.

Developers’ rationale that they do not have jurisdiction to make improvements to city intersections is not sufficient. Growth they are planning will affect Rockville and Gaithersburg. Those cities need as much data as possible to plan for the future.