The short answer is that urban planter boxes with wheels can be easy to roll over uneven pavement, but only when the wheels and planter are chosen for that job. A standard decorative planter with tiny hard plastic casters will often catch on cracks, expansion joints, raised concrete edges, cobblestones, brick pavers, tree roots, and curb ramps. A heavy-duty planter with large rubber or pneumatic wheels can handle many of those same surfaces with far less effort.
Wheel size is the biggest factor. Small casters, usually 2 to 3 inches, have very little clearance. Even a half-inch lip can stop them. Larger wheels, roughly 5 to 8 inches or more, roll over bumps and gaps more smoothly. Soft rubber or pneumatic tires absorb vibration and grip better than hard nylon or metal. Swivel casters make steering easier, but cheap swivel casters can shimmy or jam. A good setup often uses two fixed wheels and two swivel wheels, with at least one brake.
Weight also matters. Once a planter is filled with soil, plants, and water, it can weigh hundreds of pounds. The heavier it is, the more the wheels press into the pavement and the harder it becomes to push over uneven surfaces. A wide wheel base and low center of gravity improve stability. Sealed bearings, thick axles, and reinforced mounting plates help the planter survive regular movement.
Surface conditions are equally important. Smooth concrete sidewalks, indoor floors, and patios are usually easy. Cracked sidewalks, gravel, grass, wet leaves, sand, and cobblestone are difficult. Curb cuts and metal thresholds can also stop small wheels. If the route includes these obstacles, consider a planter with high ground clearance and wheels that can handle outdoor terrain, or move the planter with a dolly instead of relying on its casters.
In short, urban planter boxes with wheels are not automatically easy to roll over uneven pavement. They are easy only when the wheel design, load capacity, and surface match. For light planters on smooth paths, basic casters may be fine. For heavy planters on rough city pavement, invest in large pneumatic or rubber wheels, brakes, and a sturdy frame. That makes rolling possible, but it may still require some effort.