Planning for Transportation Disruptions

Thursday - July 6 2023, 00:13 UTC - 1 year ago

Planning is a central mission for state and metropolitan transportation agencies. Agencies develop a detouring plan for each bridge case of a structural failure or service disruption and manage rerouting traffic, which can cause safety and access problems. Traffic disruptions like failure of a major bridge can have longer-term implications such as a “permanent shift in daily mobility patterns”.

Planning is a central mission for state and metropolitan transportation agencies. Traditional long-term planning focuses on anticipating and preparing for growing and shifting transportation demand patterns. These changes are driven by regional and national economic and population trends.

Shorter-term planning is about ensuring mobility and safety during service disruptions. These events can include construction, major scheduled events like music festivals, traffic incidents such as crashes and hazardous material spills, emergency evacuations, and events like the I-95 bridge collapse in Philadelphia. Agencies have limited resources, so they typically set priorities based on how likely a given scenario is, its potential adverse effects and the countermeasures that officials have available.

For bridges, the Federal Highway Administration sets standards and requires states to carry out periodic inspections. In addition, agencies develop a detouring plan for each bridge in case of a structural failure or service disruption. Major bridges, such as those at Mississippi River crossings, are crucial to the nation’s economy and security. They require significant planning, commitment and coordination between multiple agencies. There usually are multiple contingency plans in place to deal with immediate traffic control, incident response and field operations during longer-term bridge repair or reconstruction projects.

When traffic has to be rerouted off an interstate highway, it can cause safety and access problems. If large trucks are diverted to local streets that were not designed for such vehicles, they may get stuck on railroad tracks or in spaces too small for them to turn around. Heavy trucks can damage roads and bridges with low weight limits, and tall trucks may be too large to fit through low-clearance underpasses. Successful rerouting requires a lot of coordination between agencies and jurisdictions. They may have to adjust road signal timing to deal with extra cars and changed traffic patterns. Local drivers may need to be directed away from these alternative routes to prevent major congestion. It’s also important to communicate with navigation apps like Google Maps and Waze, which every driver has access to. Route choices that speed up individual trips may cause serious congestion if everyone decides to take the same alternate route and it doesn’t have enough capacity to handle the extra traffic.

In some cases, traffic disruptions such as bridge closures can have long-term implications. When the I-95 bridge in Philadelphia collapsed, people simply took the disruption as a given and then found alternate routes or adjusted their trip times. The independent study commissioned by the Pennsylvania Department of Transportation found that a significant portion of those vehicles never returned to the I-95 corridor. Some described it as a “permanent shift in daily mobility patterns”.