A pedestrian scramble is a a type of traffic signal, in which all vehicle traffic is halted, and pedestrians can cross an intersection in all directions, including diagonally. It essentially turns an intersection temporarily into a pedestrianized area.
These have been around since the 1940s, and are starting to become popular in various large cities around the world. They go by a large number of names depending on their location. They were originally popularized by American traffic engineer Henry Barnes, so they are sometimes called a 'Barnes Dance'; in America they are more recently called 'exclusive pedestrian interval' in techspeak or a 'pedestrian scramble' in common parlance. In Canada they are more likely to be called a 'scramble intersection' or 'scramble corner', while in the UK they are often called an 'X crossing' or a 'diagonal crossing'.
Scrambles are unpopular with city managers in America -- and most other countries -- because they stop the cars from moving, and this is the cardinal sin of modern traffic engineering. Granted, they can be hard to run efficiently, as shutting down intersections in all directions can cause serious disruption to vehicular traffic, but when properly planned they can speed up overall travel times (when taking both cars and pedestrians into account), and increase pedestrian safety. They are most common, and most useful, in cities with good railway systems, which tend to disgorge a large number of pedestrians into the city center on a predictable schedule. Japan, for example, has over 300 pedestrian scrambles, many at the outlets of train stations.