Frederick sits at a crossroads in western Maryland, where the farmland of the Monocacy Valley meets the first ridges of the Catoctin Mountains. I-70 runs east-west along the south side of the city toward Baltimore and Hagerstown, and I-270 heads south toward Gaithersburg, Rockville and Washington. US 15 runs north-south as a freeway through the city toward Gettysburg and Leesburg, and US 340 heads southwest toward Brunswick and Harpers Ferry. US 40 follows Patrick Street west through the Golden Mile and over the mountain toward Braddock Heights.
Inside the city, Market Street and Patrick Street cross at the heart of the historic downtown, with Carroll Creek Linear Park running through it. MD 26 runs east as Liberty Road, MD 355 heads south toward Urbana and MD 85 serves Ballenger Creek. The I-270 commute is the defining feature of driving here, with heavy traffic every weekday morning and evening. Downtown has narrow streets, rowhouses and public parking decks, while the outer neighborhoods have driveways and garages. The climb west on I-70 and US 40 over South Mountain is long and steep.
Frederick Municipal Airport serves general aviation, and most airline travelers drive to BWI or Dulles. TransIT buses serve the city and county, and MARC trains run from Frederick toward Washington. Fort Detrick, an Army installation, sits on the city's northwest side. Most people drive, many with long commutes, so a repair at home or work saves real time. Weekend traffic on US 15 toward Gettysburg and US 340 toward Harpers Ferry picks up in fall foliage season.