Are Sequential Indicators Legal in the US?

Conditional

Sequential turn signals, which sweep in the direction of the turn, are legal in the US as long as they meet federal standard FMVSS 108. NHTSA amended the rule in 2013 to specifically allow the progressive sweep, provided the lamp still meets color, brightness and flash-rate requirements.

Why?

For years the sweeping "sequential" signal sat in a gray area, but a 2013 update to FMVSS 108 expressly permitted turn signals that illuminate in sequence, as long as the overall lamp still performs like a compliant signal. So the animation itself is not the problem.

What still has to be right is the fundamentals: the signal must show amber at the front (red or amber at the rear), reach the required intensity, and flash within the mandated rate. A retrofit that dims the lamp, changes its color, or flashes too slowly or quickly is non-compliant regardless of the sequential effect.

Factory sequential signals on modern cars clearly meet this. A cheap aftermarket module that degrades the lamp's output or timing does not. So sequential indicators are road-legal in principle; the quality and compliance of the specific setup is what decides it.

What decides if it's legal

Turn signals must meet federal standard FMVSS 108.
Sequential (progressive) turn signals have been federally permitted since a 2013 rule change.
The lamps must still show the correct color and flash within the required rate.
Front signals must be amber and rear signals red or amber.

Does it depend on your state?

The FMVSS 108 standard is federal, so a compliant sequential signal is legal nationwide. The variable is the specific product: it must keep the correct color, brightness and flash rate.

Related legality guides

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Sources

This page is general guidance, not legal advice, on the rules in the US for sequential indicators. The detail varies by exact vehicle and changes over time - confirm with your insurer and the EPA, NHTSA and your state DMV before modifying.