Free flowing traffic good for babies' health - study based on ET startup dates

A study using data from several northeastern tollers before and after E-ZPass electronic toll collection (ETC) finds the reduced tailpipe emissions from free flowing traffic produces a marked improvement in infant health. The study published by the National Bureau of Economic Research - despite its name it's a non-governmental outfit - used before and after ETC data from locations near some 98 toll plazas of the Pennsylvania Turnpike, Garden State Parkway, New Jersey Turnpike, Atlantic City Expressway, and Port Authority New York New Jersey (see map below).

The study is authored by Janet Currie and Reed Walker of the economics department of Columbia University.

They write: "Our results suggest that policies intended to curb traffic congestion can have significant health benefits for local populations in addition to the more often cited benefits in terms of reducing travel costs....nationwide reductions in prenatal exposure to traffic congestion could reduce preterm births by as many as 10,800 annually, a reduction that can be
valued at $557 million per year. Since we have focused on only one of the possible health effects of traffic congestion, albeit an important one, the total health benefits of reducing pollution due to traffic congestion are likely to be much greater."

The study tracked the dates when electronic toll collection began and took advantage of the quick improvement in traffic flow resulting from the uptake of transponder tolling to measure the relationship between the reduced tailpipe emissions from free flow and the health of small children nearby.

Premature births were reduced by 10.8% and and low birth weights by 11.8% within 2km (1.2 miles) of toll plazas.

The introduction of E-ZPass was used as the focus of the study because of its quick effect in reducing traffic congestion, not allowing time for confounding factors - such as changes in social and economic makeup of an area or in health care. Control groups were surveyed away from the influence of toll plaza traffic.

Freer flowing traffic reduces emissions of nitrogen oxide, particulates, hydrocarbons and carbon monoxide (CO) substantially as compared to stopping and starting.  CO levels seems to be a major factor in infant disease, the paper says.

The study used data on the dates and locations through New Jersey and Pennsylvania where electronic tolling was introduced in the period 1997 through 2001. It used toll authority estimates provided at the time of reductions in delay time at the toll plazas.

The study uses quite complex procedures and a number of 'robustness checks'.

They write: "The strength of our approach is that our estimates are based on a credible natural experiment rather than correlations between proximity and outcomes. Importantly, our results are robust across a variety of specifications, providing reassuring evidence on the credibility of the research design."

Results are generally consistent with other studies using different methodologies, the authors say.

Copy of the report:

http://www.nber.org/tmp/30125-w15413.pdf

TOLLROADSnews 2009-11-04