Street curb height is tolerable when it's between 2 and 4 cm. Most of the street curbs in Amman city are very problematic, unpleasant and even dangerous.
It is interesting that in many cities arround the globe most of the street curbs are built at the height of 0 cm or 1 cm which is much better solution, more accessible, and less dangerous. Also, it is much more pleasant and “normal” to cross the street with such curbs.
As for street crossings, the standard for building lowered curbs at street crossings should be 0 cm; not only for obvious reason.
Most of Amman street curbs are built with a 20 cm height, even higher, with a disconnected network of pedestrian movement.
Street curb form an important element in the urban design of the city. With a more appropriate curbs the pedestrian network will be improved, and the citizens will have a more pleasent pedestrian movement.
We keep investing our resources in building our pedestrian network and it still fail to serve the pedestrians. The problem have many dimentions but a proper street curb height need to be enforced in order to get a friendly height for the pedestrians.