What does this Swiss black on yellow rectangular traffic sign with a symbol looking like a darts missile mean?

I’ve seen this traffic sign in Switzerland. What does the second panel from the top mean? The panel is a rectangle, maybe 1½ times wider than high, depicting on the left a symbol that looks like a darts missile drawn within a rhombus, and on the right the text ►1,8m◄. The latter may indicate a maximum width but there is a different panel for that, so I expect the meaning to be a bit different.

traffic sign

I could not find this sign on this list of traffic signs in Switzerland and Liechtenstein.

Something is only permitted with AWD when having permission from the municipality of Ennenda, but what?

A few km away I saw the panel again, with the same symbol on the left, but on the right a maximum mass (12 t) rather than a maximum width:

another panel