When parking on a two-way roadway, how close must the vehicle's right-hand wheels be to the curb?

When parking on a two-way roadway, the correct distance for a vehicle's right-hand wheels to be from the curb is 18 inches. This regulation is established to ensure the vehicle is parked close enough to the curb to avoid obstructing traffic while still providing sufficient space for pedestrians and other vehicles. Being parked too far from the curb can create hazards and impede the flow of traffic, particularly in narrow roadways. By adhering to the 18-inch guideline, drivers help maintain safety and accessibility on the road.

The other distances provided are not aligned with the standards set by traffic regulations, thus making them inappropriate as answers. Following the specified measurement is critical for compliance with local parking laws and contributes to overall road safety.