Final answer:
Recreational vehicles are most similar to motorhomes or travel trailers and should be treated as such in urban planning and transportation infrastructure, whilst considering factors like size, maneuverability, and parking.
Step-by-step explanation:
Recreational vehicles (RVs) should be treated most similarly to other large vehicles used for personal leisure, such as motorhomes or travel trailers. These vehicles combine transportation and temporary living quarters for travel, recreation, and camping. In urban planning and transportation infrastructure, RVs must be considered for aspects like size, weight, maneuverability, and parking. The design problem you've mentioned — to "Design a commuter vehicle that is environmentally friendly, acceptable to a typical commuter, and compatible with existing transportation infrastructure" — requires understanding these factors as well as the unique needs of a vehicle intended for both transportation and habitation.
When designing such vehicles, aspects like fuel efficiency, low emission technology, and the ability to navigate and park in areas designed for standard automobiles are essential. This includes considering the footprint in urban environments and the compatibility with facilities like campgrounds, which are specifically designed for RVs.