Bus Size Restrictions:    

 A. Large Buses: pose a substantial issue even in large cities.
      1. Large cities: 
            a) some narrow or dead-end streets are too difficult for large buses.
            b) regulations specifically prohibit even brief blocking of streets.
            c) sensitive areas may require special parking & access permits

      2. Small Buses & Vans: Small towns usually recognize their access issues and may prohibit tour vehicles in some areas, BUT, OTOH, most wisely provide special bus parking lots & convenient temporary off-loading & loading spaces near their tourist sites.

Anecdote: Jackson, Wyoming, USA: is a gateway town to Teton National Park & Yellowstone National Park with summer tourist travel in the millions. Large tour buses may briefly drop & unload passengers at the Town Square and then quickly move to a BUSES ONLY parking lot a few blocks away.

      3. National Parks etc: may NOT provide access to small  roadside sites & trailheads, yet provide large bus & tourist parking at major sites (think Old Faithful Geyer in Yellowstone NP)

B. Small buses or tourist vans: usually have much easier, flexible access & parking even at the most popular Tier 1 sites and certainly to Tier 2 & 3 sites large bus tours must avoid.

NOTE: Access & parking are often easier at early arrival times. BIg tour buses get late start tending to arrive around 10 am & depart by 3:00 pm. More nimble van tours get to busy sites on opening.