The Benefits of Slower Traffic, Measured in Money and Lives

kade rechteroever

An unfortunate case study in political inaction.

In May 2014, three school kids in New Brunswick, New Jersey, were hit by a car on Livingston Avenue while in the crosswalk. They were each injured—one seriously—and rushed to the hospital. A cell phone video taken at the scene is pierced with anonymous screams.

Fortunately, according to news reports, the kids recovered. Unfortunately, the trauma they and their families endured is all too common on the streets of U.S. cities. What makes the situation in New Brunswick so much more regrettable is that city leaders knew about the safety hazards on Livingston Avenue but hesitated to change traffic patterns for fear of offending drivers.

That’s the frustrating conclusion one gets from a new case study about implementing a road diet on Livingston. The analysis finds that the safety benefits of reducing automobile space and speeds on the street would far outweigh any losses from driver delay. But the report’s authors state that officials were concerned from the start about upsetting the car-centric status quo:

This was expressed in an early meeting with city staff. There was a desire to complete the work prior to the start of a mayoral election campaign, since the plan was seen as controversial and would likely be opposed by voters. 

An earlier version of this same report was presented to the city back in March 2014. Officials praised its findings to the press and spoke of doing whatever it takes to make street safety a priority. But they didn’t take any urgent measures, and two months later the children were hit.

Safety gains against traffic costs

Livingston Avenue is a major four-lane road feeding into central New Brunswick, New Jersey, a college town home to Rutgers University. It has lots of rush-hour traffic—14,000 cars in the morning and up to 18,000 in the evening—and lots of pedestrians, too. Drivers seldom heed the 25 mph speed limit, and the result is that Livingston has a higher rate of pedestrian crashes than other roads in the same county.

One way to improve safety on this type of urban street is through a road diet. That would typically mean converting the avenue’s four travel lanes into three: one in each direction, and a center turn lane, with any leftover space going to curb parking and perhaps bike lanes. It would reconfigure Livingston Avenue from this …

… into something more like this:

Case Studies on Transport Policy

There’s overwhelming evidence that road diets reduce collisions, with some federal studies suggesting an average decline of 19 percent in places like New Brunswick. Of course, these safety upgrades tend to result in slower traffic, a price public officials are often reluctant to pay. So a research group led by Robert Noland of Rutgers set out to weigh the congestion costs against the safety benefits as directly as possible.

Using traffic simulations based on real traffic counts, Noland and collaborators measured changes in vehicle delay and travel times that would occur in the aftermath of a road diet on Livingston Avenue. They found that level of service—a standard metric of intersection delay—barely budged. All told, the traffic impacts amounted to two or three minutes of total delay and maybe one or two more minutes of travel time, depending on morning or evening rush hour and the precise configuration of the road diet:

Case Studies on Transport Policy

Against these modest inconveniences to drivers came clear benefits to pedestrian safety. Between 2007 and 2009 there had been an average of 38 reported crashes and 18 reported injuries a year, according to the researchers. Assuming the average 19 percent decline in crashes after a road diet, that would lead to roughly seven fewer crashes and more than three fewer injuries each year.

As a final step, Nolan and company converted all the costs and benefits into monetary figures—using standard guidelines on the economic costs of delay to business and personal life, as well as conventional (if crude) estimates on the social value of a road injury or death. They estimated the costs of implementing the diet, too. (They left out some costs, such as more traffic on alternative routes, as well as some other social benefits, such as less overall air pollution.)

When the researchers crunched all the numbers over a 20-year lifespan of the road, they found a “large positive net present value” in every modeling scenario, ranging from $2.6 million to $37 million. They conclude:

Our results have shown that implementation of a road diet, consistent with a complete streets policy along Livingston Avenue will result in some extra delay to traffic both along and within the corridor. However, the costs of the delay to traffic are less than the large benefits associated with the reduction in traffic crashes, based on a cost/benefit analysis.

The high costs of inaction

Numbers like these, convincing in their own right, still pale in the face of the real human harm a dangerous road can inflict. After the school children were hit on Livingston, community members learned about the study that had come out just two months earlier and demanded that a road diet be implemented on the avenue. New Brunswick Today detailed the public outcry at great length back in May 2014:

Just a day later, hundreds marched from the scene of the crash to City Hall, where the City Council was scheduled to meet, holding up signs with slogans like "Protect [our] Children!" and "Justice For The Kids." …

The next night, at the meeting of the Middlesex County Board of Chosen Freeholders, many of the same protesters seized on the proposed "road diet" initiative, which was suggested in a report issued by the Rutgers Voorhees Transportation Center in March.

The protests were largely a family event, with children making up more than a third of the 300 or so protesters.

And they got results: County Freeholder Director Ronald Rios read from a prepared statement promising major changes "within 30 days" to two of the most dangerous sections of the four-lane road that has become the focus of so much attention in recent months.

The city did make some swift safety changes to two intersections on Livingston after the protests—proving, in effect, that it was capable of enacting such measures in a timely fashion. In their updated report (though not in their original, which can still be found on the city website), the study authors note with some sad irony that officials had been concerned about an uproar over the traffic impact of a road diet, and instead got an uproar about the safety hazards that very diet would have addressed. Here’s how they put it:

Public officials should be less timid in their approach to implementing positive changes that improve safety and walkability, even at the expense of potential delays to traffic. 

In a sense, then, the case study of Livingston Avenue is less about the traffic costs of a road diet and more about the social costs of political inaction. It’s not clear those lessons have been learned. Livingston still hasn’t received the sort of road diet outlined in the original study. In August 2015, the city held its second public meeting about a full implementation of a road diet on the street; at the time of that meeting, at least, no further ones had been scheduled.

Eric Jaffe
Citylab 02-10-2015