Fixing a severe local problem may be worth creating a minor global problem. Having good data about how things are used, like the traffic data for the intersection, is the key to making these decisions. You have to be clear about the pros and cons of each end of the trade-off, and make the best decisions for the feature in relation to the entire product. Sometimes global consistency is the right choice. Sometimes the best thing is to optimize locally.
Consistency is great because people like predictable things.
They will feel comfortable when they can rely on different parts of your product to do exactly what they think it will do. A common Web site design mistake is taking an existing UI element from HTML and optimizing it for one Web site. An example is the drop-down list box provided by HTML for picking from a list of choices. The standard behavior is that the user has to pick an item from the list, and then click an OK button to confirm the choice. Some Web sites use Java script to make the drop-down automatically confirm the choice, saving the user the extra click of hitting OK .