Two-Way Bridge Clearance Calculator

Enter six decimal-foot readings for each travel direction. The calculator follows each lane through both ends of the bridge and produces a separate feet–inches result for each direction.

Two-way layout: Each travel direction uses six readings: EM left, crown, and EM right at the entering and exiting ends of the bridge. See the RCOC Low Clearance Signs guidance.

Quick reference

What the MMUTCD says

Section 2C.25

Advance warning: Use a W12-2 in advance when actual vertical clearance is less than 14'-6", or less than 12 inches above the statutory maximum vehicle height, whichever threshold is greater.
Displayed clearance: Show the clearance to the nearest inch without exceeding the actual clearance. A reduction of up to 3 inches should be used where frost action can change the clearance.
Overhead signs: W12-2a or lane-specific W12-2b signs may supplement the advance sign. Use additional overhead signs where clearance varies greatly, and keep the advance legend consistent with the lowest overhead value.

August 7, 2026

Michigan project-use date: The 2025 MMUTCD applies to applicable MDOT-let projects beginning with this bid letting. Table 1B-1 items are coordinated statewide.

January 18, 2029

Low-clearance target date: Five years after the 11th Edition's January 18, 2024 effective date for the W12-2 advance-sign requirement and variable-clearance overhead-sign guidance.

Sources: MUTCD Table 1B-1 and MDOT Design Advisory 2026-02.

Field measurements

A two-way bridge uses 12 readings total—six for each travel direction.

Direction 1

Travel Direction 1

6 readings

Entering end

EM left (ft) —

Crown (ft) —

EM right (ft) —

Exiting end

EM left (ft) —

Crown (ft) —

EM right (ft) —

Existing clearance sign posted?

Direction 2

Travel Direction 2

6 readings

Entering end

EM left (ft) —

Crown (ft) —

EM right (ft) —

Exiting end

EM left (ft) —

Crown (ft) —

EM right (ft) —

Existing clearance sign posted?

Directional results

The sign legend includes the 3-inch frost/resurfacing allowance and is rounded down to a whole inch.

Enter all six readings for Travel Direction 1.

Enter all six readings for Travel Direction 2.

Important: “Sign legend” and “sign required” are separate. The standard threshold is checked against the actual measured minimum before the 3-inch allowance. When the threshold is not met, the calculator recommends removing an existing sign; confirm that no separate site-specific requirement applies before removal.