A few days ago, Metro planners wrote that about two-thirds of Metrorail trips cross county or state boundaries. What about the trips that don’t?

All maps by the author.

Commenter Richard said he was surprised there were any intrajurisdictional trips in Prince George’s County, given the lack of development around the stations. To understand it, I delved deeper.

This analysis, and Metro’s, consider the jurisdictions of DC, Montgomery, Prince Georges, Arlington, Alexandria, and Fairfax County. Because the morning peak period best represents the commute trip, my analysis considers the morning peak only.

Metro’s data only counts a trip as cross-jurisdictional if it ends in a different jurisdiction from where it started. But my analysis also excludes trips like Prince George’s Plaza to Suitland, which cross a boundary and then return to the original jurisdiction.

Prince George’s County

In the case of Prince George’s, there are four isolated segments with three or four stations each. These short segments don’t have a lot of synergy to collect the longer trips Metro riders typically take, and there’s not a lot of transit-oriented development around any of the stations. Not surprisingly, few trips stay entirely within Prince George’s.

All graphics by the author.

In Prince George’s the Blue Line section from Capitol Heights to Largo has the highest intrajurisdictional rate. During the AM peak, 3.47% of trips that start at one of those stations ends at one of them. The Greenbelt end of the Green Line is next, with 3.00% of trips staying within that section.

On the other end of the line, between Southern Avenue and Branch Avenue, 2.49% of trips that start there also end there. The New Carrollton branch trails, with just 1.24% of riders staying within that section.

Why would people take trips between these stations? Some passengers are likely making “bridge” trips connecting between two bus lines. In some of the other jurisdictions, those trips might also happen on the bus network, but none of the Metro lines in Prince George’s have much parallel bus service. Additionally, while there’s not much development, there is enough to generate some trips that don’t cross the county line.

One more methodology note: There are some border stations which are in two jurisdictions, like Capitol Heights on the DC/Prince George’s boundary. I counted all trips between Capitol Heights and one of the stations toward Largo as a Prince George’s trip, and any trip between Capitol Heights and a station in DC as an intra-DC trip. The same went for the other border stations: Friendship Heights, Southern Avenue, Takoma, and Van Dorn Street.

Montgomery County

Next door, in Montgomery County, the numbers are quite different. Both ends of the Red Line extend into Montgomery County, but between Silver Spring and Friendship Heights the line is in the District.

The Glenmont end has 5 stations, counting Takoma, which is just a block inside the District. Glenmont, Wheaton, and Silver Spring are all major bus hubs. Silver Spring is a major jobs center, which probably helps draw intrajurisdictional trips.

On the other side of Rock Creek, the Red Line penetrates deep into Montgomery County, running all the way from Friendship Heights out to Shady Grove. Bethesda and Medical Center are home to many jobs, and Rockville and White Flint have growing employment markets.

In terms of intrajurisdictional ridership, the Shady Grove end does better: 22.70% of trips that start within that segment stay there. Only DC has a higher rate of intrajurisdictional trips. The Glenmont end of the line sees 5.13% of trips stay within the section.

Fairfax County

Across the Potomac, Fairfax County has four disconnected segments. We’ll discount the Huntington end, since Huntington is alone in Fairfax. The next station on the line, Eisenhower Avenue, is in Alexandria.

The other sections consist of the Blue Line between Franconia-Springfield and Van Dorn Street, the Orange Line between Vienna and West Falls Church, and the Silver Line between Wiehle Avenue and McLean.

The Franconia end of the Blue Line really doesn’t have a chance to get any synergy, with just two stations. Van Dorn Street is technically in Alexandria, but, like Takoma, is right on the boundary. On the Orange Line, Fairfax has been trying to build TOD around its stations, but the three stops are all in the median of I-66. The Silver Line, on the other hand, serves the major jobs center in Tysons and extends far beyond to a park-and-ride at Wiehle Avenue.

Even though the Silver Line had only been open for about three months in this data set, it performs the best within Fairfax. Of the trips that start at one of the five stations, 6.05% are to another of those stations, which is almost a full percentage point above the Glenmont end of the Red Line.

Somewhat surprisingly, the Franconia section of the Blue Line within Fairfax comes in second place, with 1.79% of trips that start at one of those two stations going to the other. The Vienna end of the Orange Line sees only 1.71% of trips that start there also end there.

Alexandria

In Alexandria, there’s a contiguous section of the Blue and Yellow lines between Braddock Road and Van Dorn Street and Eisenhower Avenue. This section contains just four stations.

Only 4.10% of trips that start in Alexandria stay within the city.

Arlington County

Like its neighbor to the south, Arlington has one group of contiguous stations in two corridors. In the north end of the county, the Orange and Silver lines serve six stations from East Falls Church to Rosslyn. The Blue Line and (south of Pentagon) the Yellow Line serve five more stations along the Potomac River between Rosslyn and National Airport.

This area includes major jobs and housing centers in both corridors, but especially in the Rosslyn-Ballston corridor.

Of the trips that start at one of these 11 stations, 13.28% stay within Arlington County. That puts the county in third place for intrajurisdictional trips in the AM peak, after DC and Montgomery’s Shady Grove branch.

District of Columbia

Finally, as expected, the District has the greatest amount of intrajurisdictional ridership. A whopping 75.83% of trips that start within the District stay there.

That shouldn’t surprise anyone, since the District has the largest contiguous section of the Metro system, the densest and most transit-served central business district in the region, and dense transit-oriented neighborhoods.

Generally, cities and counties that have encouraged transit-oriented development around their stations, like Montgomery County’s west side and Arlington, have more intra-jurisdictional ridership than others. But simply having more stations and track mileage also has a lot to do with it.