No Cars/Cars?

The sign outside my hotel in the Old Quarter of Hanoi might suggest that vehicular traffic is prohibited, i.e. only pedestrians and maybe scooters allowed. After walking the length of the street, I know there is a similar sign, facing the other way, at the other end. But this street (Hang Bac) is always clogged with traffic. Maybe the sign means no cars, but buses (shown above) are allowed? Or maybe the sign is positioned so far from the corner that no one can see it? Or, perhaps as is true with many things in Vietnam, the sign is just a suggestion.