Sorry, but at first, I could not understand the question. Finally, light was made: tides are the point. Intertidal zone in Malaga may be about one inch broad, and I can't figure how to drive in such a space... But about Donax, I have to say that once they was very abundant and consumed with delight, but now they have almost disappeared. We still consume it actively, but now they come from Italy. The reason has nothing to deal with traffic, but with the six million tourist we host along all year, wich you can usually find laying on the beaches (not all at the same time, of course...) The ecological impact of this oversized population gets ride of Donax, as well as many other molluscs (and marine life). Not only for people themselves, but for all that is associated, specially the increase of residual waters and other contaminants. So here, driving at the beach has no significant effect. Best regards, Alfonso Pina Malaga Spain