“This cart is at your service
Contact person: [#]
Your satisfaction guaranteed”

The promise of service yet to be delivered. Consider the ways in which this is more effective than were a person standing next to it (or standing alone without a cart). Compared to someone standing and vocally advertising a comparable service, how is this superior? Inferior?

Considering the placement of the cart in the path visual/physical path of pedestrians, and the likelihood that one will glance at it in recognition of having to take measures to avoid it, the odds they will read its service message is high – a mild inconvenience/obstacle for most, an ideally placed service proposition for a few.