What is the difference between the following signs?

- Sign 505 indicates a stop for private buses. Sign 506 indicates a Tramway stop.
- Sign 505 indicates a Tramway Stop. Sign 506 indicates a stop for Public bus transport.
- Correct answer: Sign 505 indicates a stop for Public Transport (Buses). Sign 506 indicates a stop for a Public Tramway.
- Sign 505 indicates a public transport stop on a Motorway (Freeway). Sign 506 indicates a public transport stop.
Why this is the answer
The correct answer in the official bank: Sign 505 indicates a stop for Public Transport (Buses). Sign 506 indicates a stop for a Public Tramway.
Both signs show a blue square with the symbol of the vehicle that serves the stop. Sign 505 shows a bus, so it marks a public transport bus stop and lists bus line numbers and destinations. Sign 506 shows a tram, so it marks a public tramway stop with the lines that call there. Neither sign refers to private buses or to a particular type of road such as a motorway.