Historically, transportation policy addressing vehicle congestion has entailed increasing road capacity. However, research consistently reveals that these policies have the opposite effect. In fact, a new study reveals that cities may be able to improve vehicle travel times by closing certain road segments completely. Using the theoretical framework of the Braess Paradox, the study’s researchers model how blocking off selective streets in downtown Winnipeg can reduce overall vehicle travel times, a change which in turn enables new car-free spaces to be reclaimed as parks or pedestrian plazas.
congestion
Ecommerce fulfillment centers increasing freight pollution, congestion in rural towns
In order to keep up with ever-increasing ecommerce demand, companies such as Amazon are building sprawling new fulfillment centers on the outer edges of major U.S. metro areas to aid in their logistical operations. While these warehouses can provide a windfall in economic development for the rural towns where they are being constructed, a recent article found that, increasingly, communities are finding these facilities are more trouble than they’re worth. Specifically, the jobs and tax revenue being generated don’t outweigh negative impacts caused by freight pollution and traffic congestion.
Cities need to move carefully to get TNC benefits
A new report examined existing research and new data on the impact of Transportation Network Companies like Uber and Lyft on U.S. cities. TNCs can have negative impacts on urban areas by contributing to traffic congestion—but, if planned and regulated properly, can find their ideal niche within urban transportation systems.
Is traffic congestion a good thing?
Transportation planners and engineers often think of traffic congestion as a problem that must be alleviated by building new roadways and widening existing ones. However, a new study goes against conventional thought to suggest that traffic congestion may actually be a sign of success for regions.
Efficient networks take work: Traffic management and Braess’ paradox
Not all roads are created equal. In fact, adding certain roads to a system can actually slow down traffic under the right circumstances. This is a fairly well known phenomenon called Braess’ paradox, named after the German mathematician who first wrote about it in 1968. Fortunately, researchers have studied this occurrence extensively and developed methods for knowing when it can happen and how to prevent it. A new study published in the Journal of Transportation Engineering lays out fairly straightforward methods to identify troublesome links.
When Waze clogs the streets, can communities close them to outsiders?
Reacting to drivers using apps to bypass clogged highways, the borough of Leonia, NJ, has decided to close most of its local roads to non-residents during peak morning and afternoon periods. Many question whether this is a wise or even legal option. In the short run, the shutdown of local roads might make residents happy; but in the longer term, residents could face worsened regional congestion as traffic is forced onto clogged arterials. In dense networks, these local roads can sometimes act like important release valves.
Traffic enforcement observations target Uber and Lyft drivers as largest offenders
A recent scan from San Francisco’s Police Department found that Uber and Lyft drivers were responsible for nearly 65 percent of traffic infractions in bike- and transit-only lanes. The overwhelming majority of these tickets, for all vehicles and for Uber and Lyft vehicles, cited San Francisco Code 7.2.72 TC (see below), “Driving in a Transit Lane,” which comes with a $69 fine. There were also three felony and 29 misdemeanor arrests associated with this traffic report, indicating more serious incidents.
A framework for determining where congestion really matters
These two things are true: 1) Travelers dislike slow traffic, and 2) slow traffic is sometimes an inescapable result of things that people do like—cities with popular destinations. Conventional transportation practice responds well to No. 1, with well-known standards for delay and capacity. Practice has no clear standards to deal with No. 2—what to do in places where speeding up cars amounts to destroying the village in order to save it. A new study of neighborhoods in Los Angeles, a place with more than a little congestion, helps fill this gap.
What HOV requirements in Jakarta can teach us about congestion
According to a new paper from three researchers at Harvard and MIT, removal of a strict High-Occupancy Vehicle policy had negative effects on traffic in Jakarta, Indonesia, the world’s second largest metropolitan area. Congestion increased even on streets with no restrictions and during times when the policy had not been in place. The decision to remove the policy provided an opportunity for a natural experiment in congestion mitigation.
Study of variable speed limits highlights the trade-off of throughput and safety
Varying a posted speed limit based on current conditions can improve operations and safety in congested work zones, a team from Missouri found. This study from the University of Missouri-Columbus explores this phenomenon in a congested work zone in St. Louis, Missouri. The findings? Results depend on whether DOTs are looking to prioritize safety over capacity.