Over the next three decades, increasing population and job growth will lead to more vehicles, more trips, and more congestion on the region’s transportation system.
How Travel Patterns and Traffic Conditions Will Change Between Now and 2040
The overall amount of driving in the region – measured in vehicle-miles traveled – is expected to grow by 25%, slightly more than population, which means that VMT per capita – a measure of how much the average individual drives – is forecast to increase by about 1%.
The increase in demand on the region’s roads by 2040 is expected to outpace increases in supply, leading to a significant increase in congestion. Total VMT is expected to rise 25% while funding constraints will limit the increase in new roadway capacity to 7%. That gap will result in a 78% increase in the number of lane-miles of congested roadway during the morning peak period.
Mode Choice: How People Choose to Travel
All Daily Trips
The modes by which people choose to travel aren’t expected to change much over the next three decades. Currently, 42% of all trips in the region are made by drivers of single-occupant vehicles, a share that will drop by only a few percentage points by 2040. Carpooling is forecast to become slightly more popular, growing in share from 41% to 42%. Trips made by non-motorized modes will also make up a slightly greater share of total trips in 2040 than they do today, while transit share will remain the same.
Although mode share is not forecast to change significantly, the total number of trips taken using each mode will grow. The number of transit trips will grow by 28%, or about 359,000 trips, for example. In 2040 the region’s roadways and transit system will have to accommodate a much larger volume of travelers than today.
Population and job growth will also lead to an increase in the total number of commute trips in the region – about 29% by 2040. However, work trips will continue to make up around 21% of all trips, and those made by drivers will continue to account for about 40% of all vehicle-miles traveled. By 2040, the share of work trips by carpool and non-motorized modes is expected to increase, from 11% to 14% for transit, and from 4% to 5% for non-motorized modes.
To address the lack of identified funding for WMATA’s future rehabilitation and maintenance needs beyond 2020, transit ridership to or through the core area was constrained to 2020 levels. When this constraint on transit trips is lifted, there is an increase of 31,000 transit work trips in 2040. This brings the transit mode share for work trips up to 24.5% from 24%.
Geographic Differences in Mode Choice
Changes in travel patterns will also vary by geography, both in terms of the number of trips taken and how trips are made. Figure 16 shows that the majority of work trips today and in 2040 are or will be made in the inner suburbs – Montgomery, Prince George’s, and Fairfax counties – which are the region’s most populous jurisdictions. The outer suburbs – Prince William, Loudoun, Frederick, and Charles counties – will see the most significant rates of growth in the total number of trips, since population and employment will be growing fastest there.
In the regional core, the majority of work trips – 58% – are made on bus and rail transit, and 13% are made by walking or biking. In the inner suburbs single driver trips account for the largest share of work trips – 63% – and nearly a quarter of works trips are taken by transit. Though the transit share is lower than the regional core, the number of transit work trips generated in the inner suburban counties is greater than that of the regional core. In the outer suburbs, more than 75% of work trips are made by single drivers.
By 2040, slight changes in mode share are expected in all three areas. In the regional core, the share of transit trips is expected to drop in favor of more walk and bike trips. In the inner suburbs, single driver trips are expected to drop slightly, while both transit and non-motorized trips will increase. And in the outer suburbs single driver trips are expected to drop, while carpool and transit trips are expected to increase significantly. Projects such as the Silver line to Dulles Airport, which brings Metrorail transit to Loudoun County, and the HOT lanes projects in northern Virginia contribute to this shift.