An exit ramp is still part of the highway and probably even more subject to safety regulation.
It’s still considered a “street display.”
Proceed with caution.
Here is an example of part of a display signage law in the the state of Connecticut, USA.
Note the part about using language that could be misinterpreted as safety warnings to drivers. It would surprise me mightily if Austria did not have similar Department of Transportation laws:
By law, outdoor advertising structures, signs, displays, and devices within 660 feet of the edge of the right-of-way of highway on the Interstate Highway system, federal-aid primary system, and other limited access highways are prohibited, except within urban areas, when their advertising message is visible from the main traveled way of the highway. Such signs and structures are prohibited outside of urban areas along these highways even if they are more than 660 feet from the edge of the right-of-way. The following types of signs may be permitted within the 660-foot area, with the approval of the transportation commissioner and subject to regulations he adopts, except if prohibited by state law, local ordinance, or zoning regulation: (1) directional and other official signs and notices, including but not limited to signs pertaining to natural wonders and scenic and historical attractions which are required or authorized by law: (2) signs, displays, and devices advertising the sale or lease of the property on which they are located; and (3) signs, devices, or displays advertising activities conducted on the property on which they are located (CGS § 13a-123).
Subject to DOT regulations and except as prohibited by law, ordinance, or zoning regulation, signs, displays, and devices may be erected within 660 feet of primary and other limited access highways in areas that are zoned for industrial or commercial use or located in unzoned commercial or industrial areas as defined by DOT regulations.
The law prohibits “unauthorized” signs within 300 feet of any state highway. These are signs that have any of the following words: “stop,” “caution,” “danger,” “dangerous,” “warning,” or “slow,” or any other word or character intended to or able to give warning or direction to or interfering with traffic, except if the transportation commissioner approves. However, municipal officers or public utilities may erect any danger or warning sign required by law or any sign designed for the protection of the public or to aid in the utility’s operation (CGS § 13a-124). The transportation commissioner may enter any property and remove any sign that does not conform to these requirements. Anyone violating the prohibitions may be fined up to $100 for the first offense and up to $500 for any subsequent offense.