What does this traffic sign indicate?

This traffic sign indicates a bridle-path specifically designed for riders. The key points regarding this sign are:

1. A bridle-path, which riders are required to use: This means that horseback riders must use this path instead of riding on the roadway.

2. A bridle-path, which may not be used by other road users: The sign restricts access to riders only, meaning other vehicles or pedestrians should not use this path.

In summary, the sign prioritizes the safety and designated space for horseback riders while keeping other road users away from that area. Understanding this helps promote safe travel for both riders and other vehicles on the road.