Detour Signs: Which Sign Goes Where, Sizes and How Many

A detour sign is any of the orange signs that lead drivers around a closed road: the DETOUR warning sign ahead of the closure, the DETOUR arrow sign at the closure, DETOUR plaques or arrow signs at every turn along the route, and END DETOUR where drivers rejoin. Most are black on orange; the plaque on route markers is 24 x 12 inches on conventional roads.

Sign	Code	Where it goes	Conventional road	Freeway or expressway
DETOUR with distance (diamond)	W20-2	Ahead of the detour, as advance warning	36 x 36	48 x 48
DETOUR arrow	M4-10	Just below the ROAD CLOSED sign, arrow toward the detour	48 x 18	(none)
DETOUR plaque	M4-8P	On top of a route marker along a numbered-route detour	24 x 12	30 x 15
DETOUR with arrow	M4-9	At turns on unnumbered roads, short or emergency detours	30 x 24	48 x 36
END DETOUR	M4-8a	After the detour ends	24 x 18	24 x 18
END plaque	M4-8bP	On top of a route marker at the end	24 x 12	24 x 12
Pedestrian, bike or combined detour	M4-9a, M4-9b, M4-9c	Where a sidewalk or bike route is detoured	30 x 24	(none)

Sizes in inches, from MUTCD Tables 6H-1 and 6I-1. The W20-2 minimum is 30 x 30 for low-speed, low-volume roads.

Route markers or DETOUR arrows

Section 6I.02 asks that every detour be "adequately marked with standard temporary route signs and destination signs." In practice there are two ways to sign one:

• Numbered route detour. Put a DETOUR (M4-8P) plaque on top of the route marker assembly at every turn and as reassurance along the way. Drivers follow "DETOUR, US 30" and an arrow.
• Unnumbered streets, short or emergency detours. Use DETOUR (M4-9) signs with an arrow at each turn, with the street name above or on the sign.

How many signs to order

Walk or drive the route and count decision points:

1. Advance warning: one W20-2 (or a ROAD CLOSED AHEAD sign) on each approach.
2. At the closure: ROAD CLOSED with a DETOUR arrow (M4-10) below it.
3. At every turn: a sign before the turn and one at it, on each direction the detour runs.
4. Reassurance: a sign after each turn and every so often on long stretches, so drivers know they're still on the detour (Section 6N.09 suggests reminding drivers on long detours).
5. End: END DETOUR or an END plaque where the route rejoins.

Double the count if the detour runs both ways, and add pedestrian detour signs if sidewalks close.

Colors

Detour signs are black on orange for planned work. For incident management (crashes, emergencies), the MUTCD allows black on fluorescent pink, so drivers can tell a temporary incident detour from a construction one.

Mistakes we see

• Signs only at the closure. Drivers get lost at the second turn.
• No END DETOUR. Drivers keep following arrows that aren't there.
• Leaving detour signs up after the road reopens. Drivers stop trusting them.
• No street name on M4-9 signs. The MUTCD asks for it above or on the sign.

What it costs

Ballpark U.S. prices in late 2026: $20 to $45 for a 24 x 12 DETOUR plaque, $50 to $110 for a 30 x 24 M4-9, $70 to $150 for a 48 x 18 M4-10, and $60 to $150 for a 36-inch roll-up W20-2. Many agencies rent full detour packages from traffic control companies for short jobs.

Where to buy or rent

Sign shops, traffic safety distributors and traffic control rental companies. Order by code and size, and ask for reflective sheeting on every sign used at night.