Maryland officials are considering a third bridge span across the Chesapeake Bay from the Annapolis area to the Eastern Shore of Maryland. During summer weekends the two existing spans are congested during peak times of travel, but seven months of the year there is usually free flow. Significant traffic congestion is generated during the week year-round by those who commute to Washington, D.C., and Baltimore from the Eastern Shore. The current spans have a toll in the eastbound direction, and there are major backups during peak times at the toll plaza. The toll is the same no matter the time of day or level of traffic.

An additional aggravation has been the closing for two years of one of the westbound lanes for deck reconstruction, which has led to lengthy backups during the now extended peak times of travel. The governor wants to use only electronic tolling, which should help the flow of traffic somewhat. While better management of the situation may help, when supply of something in great demand is reduced, the price of it goes up; in this case the higher price is greater time and operating costs of stop-and-go traffic for motorists crossing the bridges.

Many are for another span as a long-term solution, but a third span would cost billions of dollars and take many years to construct. Some also argue that an additional span will “induce demand,” and congestion will reoccur. The idea of “induced demand” is a variant of “supply creates its own demand,” attributed sometimes to marketing of new products or services that didn’t exist before. But supply does not create demand; too many businesses don’t survive because of little or no demand no matter how much supply is produced. Besides, supply of road capacity is certainly not a new product, and demand in this case already exists because of the timing of work and leisure travel to “downy o-ocean.”

When road capacity (supply) is added, the price of travel decreases. Lower prices for travel encourage more consumption of road capacity or “induced traffic.” If capacity is again exceeded during peak times, then congestion reoccurs. So, yes, congestion can reoccur, but not because demand has been created or induced by supply, but because lower prices encourage more consumption of road capacity.

Some writers describe the process of congestion, adding road capacity and eventual reoccurring congestion as leaving us back where we were before, but that’s definitely not the case. Induced traffic means that the lower price has enticed existing motorists and new ones to travel more to economic and other opportunities — which is a good thing. Also, free flowing traffic may occur at least for a while. Demand could expand over time because of population and income growth.

Another scenario makes clear that road supply doesn’t induce demand. You could travel for miles in Western Maryland, West Virginia or the western U.S. and note that an additional lane won’t bring about congestion. Actually, another lane reduces price of travel slightly from an already low price, demand stays the same, resulting in little or no additional traffic.

It’s also been suggested that driverless vehicles would improve the flow of traffic across the bay, thus dispensing with the need for a third span. Driverless vehicles, except in experimental, controlled lanes and environments, are 10-20 years off, if ever, and not everyone will want one. In other words: Don’t wait for them before heading to the beach again.

So, if a third span across the bay is built, would it become congested during summers? Probably at some point, but whether a third span is built or not, tolls could vary to ration traffic better than waiting in long backups does. The Maryland Transportation Authority suggests motorists cross the bridges during off-peak times; tolls varying by time of day would actually prompt them to do so, and could be implemented soon.

Also, Eastern Shore vacation home owners and management companies may learn to offer incentives, such as reduced rental fees for late evening and early morning arrivals and departures. Businesses could vary their employees’ work hours. Such incentives would further spread the peak travel times and reduce peak traffic.

Z. Andrew Farkas (andrew.farkas@morgan.edu) is director of the National Transportation Center at Morgan State University.