There are two options.

1. An arrow pointing downward left or right indicating the correct side on which to pass. The advantage here is that the symbol is more likely to be understood by unfamiliar drivers.
2. A blue striped signal, which can often mimic the striping of the device that it supplements. The advantage here is that the light in its chevron form can tell drivers to pass on either side, or on neither side as at a dead end.

3C1. Pass on One Side. These examples are devices telling drivers to pass on the left-hand side of an obstruction. Of course, the right-hand versions are mirror images.

OM-3R		Drums		Barricades

Below left is a drum that displays oblique striping as a barricade would. While the greatest use of drums is in construction zones, drums used instead for incident management would presumably be pink (below right) to match incident management signs.

Drums proposed

3C2. Pass on Either Side.

OM-3C	Drums		Barricade

Below are two more possibilities. Longer barricades might use all three signals.

Barricades

3C3. Dead End. The OM-3D extends the analogy between the striping of barricades and the striping of other signs in the OM-3 series.

OM-3D proposed	OM4-2	Drum	Barricade