Traffic condition in Bangkok have deteriorated rapidly in recent years and are now arguably the worst of any large urban area in the world, In 1989 the average travel speed on main road in the Bangkok metropolis was 8.1 km/hour. (5mph). Traffic has slowed since then and is often slower than the projected 2006 travel speed of 4.8 km/hour (3mph). It is increasingly difficult to identify peak travel periods for congestion now persists throughout the metropolis from early morning to late evening.