Impact of flooding on truck movement in Metro Manila, Philippines

Flooding in Metro Manila is a perennial problem given the frequency of typhoons hitting the country every year. When a flood occurs along major roads, vehicular traffic usually results in a standstill, causing major disruptions that impede the flow of people, goods and services. The study assessed the impact of flooding in terms of changes in the route of trucks under reduced road capacities and design speeds while considering the impact on vehicle-distance travelled, vehicle-hour travelled, average travel speed, among others. GPS data loggers were used to track the movements of selected trucks during normal conditions to determine their regular routes. Face-to-face questionnaire survey was also conducted to know the behavior of truck drivers during flooding incidents. Scenario modelling under flooded conditions was developed for a typical day during which trucks are allowed to operate on the road under a 5-year and 25-year flood incident. On a metro-wide scale, during flooding, the vehicle distance travelled (VDT) and vehicle hour travelled (VHT) may not necessarily increase since some vehicles, including trucks, may not be able to travel or are unassigned resulting in a lesser number of them on the road, effectively reducing VDT and VHT. Furthermore, higher VDT during the 5-year flood event were observed compared to the 25-year flood event since there are still many vehicles travelling during the former in search of alternate routes resulting in more distance travelled. However, focusing only on flooded roads, the travel time spent by vehicles increased in order for them to reach their destinations even with reduced number of vehicles traveling on these flooded roads.