Highways come in all shapes and sizes. Some are long and some or short. Some climb through great heights via mountain ranges, while others barely register above sea level. Most of them in the western world are paved, though a few dirt and gravel roads still exist in some parts. The State of Washington has -- what I believe to be -- one of the most unique highways: the beach.
Yes, you can drive on most Washington beaches and those beaches are part of the state's highway system. Run afoul of numerous laws and don't be surprised if you're pulled over and handed a ticket!
From the standpoint of convenience, being able to drive on the beach is a cool thing. No need to find a parking area and then have to tromp down rutted paths to the ocean's edge. You can park so close that the waves lap at your tires! In fact, if you're not paying close attention, the sea can swallow you up relatively fast.
Since moving to Ocean Shores (and many times previously), I honestly admit that I have driven on the beach numerous times -- heck, almost daily. While I certainly enjoy the accessibility, I worry about the environmental costs. I can't imagine that all the oil and noxious gasses that vehicles regularly emit is conducive to a clean and healthy ecosystem. I worry that the human desire for convenience is befouling the very beauty we seek to take in.