Former Route Numbering

From 1973 until June 29, 2025, original Metrobus routes followed the rules below: ^{[1] [2]}

• Metrobus routes in Washington, D.C., have either a two digit number (31, 42, 64, etc.) or a letter followed by a number (A2, S2, X8, etc.).
• Metrobus routes in Montgomery County, MD, have a letter followed by a number (C4, Q4, Z6, etc.).
• Metrobus routes in Prince George's County, MD, have a letter followed by two numbers (F12, J12, P12, etc.).
• Metrobus routes in Northern Virginia have one or two numbers followed by a letter (1A, 16C, 29N, etc.).

Odd-numbered routes are typically part-time variants of even-numbered routes. At one time, odd numbered routes were express routes, but that distinction has been abandoned. Most Maryland and Washington, D.C., routes are grouped by their first digit. When this system was laid out in 1936, the following clustering was used:^{[ citation needed ]}

Legacy Route Crosswalk

In the transitioning to the 2025 Network, launched on June 29, 2025 during Better Bus Network Redesign, it was replaced the 50-year-old radial system with a modernized, sector-based grid. Under this framework, familiar neighborhood links were evolved to meet modern travel patterns. For instance, the Fort Totten and Chillum area previously served by the K2 now uses the P35 for the Sargent Road corridor, while the Greenbelt and NASA links once found on the G14 have been absorbed into the P32. Similarly, long-standing routes like the W4 and V7 in Southeast were streamlined into the unified C21 loop, and the busy 70 and 79 corridor was upgraded to the high-frequency D40 and D4X spine to ensure more reliable service along Georgia Avenue.

While many historic route numbers were retired, their service corridors remain active under four core transition categories:

The following "crosswalk" identifies how major historic streetcar corridors, radial city routes, and lettered Maryland/Virginia lines have been integrated into the 2026 sector-based grid.