Transportation System Performance-HOV Lanes and TDM

Two HOV lanes operate in the Boston metropolitan region: a reversible, barrier-separated lane on I-93/Southeast Expressway that connects downtown Boston and Route 3 at the Braintree split interchange, and a southbound, buffer-separated lane on I-93 North that approaches Boston from the north. Click here for a map of the limits of the HOV lanes.

Description of the HOV Lane Facilities
The 5 1/4 -mile-long I-93/Southeast Expressway HOV lane has one terminus south of Columbia Road (Exit 15) and another located south of Furnace Brook Parkway (Exit 8) in Quincy just north of the Braintree Split (Exit 7) and Route 3 (Exit 20). On weekdays (except some holidays), it is open to northbound traffic between 6:00 AM and 10:00 AM and to southbound traffic between 3:00 PM and 7:00 PM. The HOV lane’s contraflow system “borrows” a freeway lane from the general-purpose lanes in the off-peak direction and converts it to a peak-direction HOV lane that is open to carpools with two or more occupants, vanpools, buses, and motorcycles.

The roughly two-mile I-93 North HOV lane runs southbound between the Mystic Avenue on-ramp in Medford and the Zakim–Bunker Hill Bridge after the I-93/Route 1 merge in Boston. The I-93 North HOV lane is open to vehicles with two or more occupants and to all motorcycles between 6:00 AM and 10:00 AM, Monday through Friday. The lane is open to all traffic at all other times.

Traffic Volumes on I-93/Southeast Expressway HOV Lane
MassHighway continuously monitors the traffic volumes of the I-93/Southeast Expressway HOV lane. Before June 1, 1999, when the occupancy rule of the HOV lane changed, the lane carried an average daily total of about 3,500 high-occupancy vehicles. The total volume increased after that date, and from 2001 to 2003 it remained stable, at a daily average of about 8,700. This volume corresponds to an estimated daily average of 33,660 persons. Approximately 95 percent of the vehicles are automobiles with carpooling passengers; the remainder includes vanpool vans, public and private transit buses, and motorcycles. (No volume data are available for the I-93 North HOV lane.)

Based on vehicle occupancy counts from an October 30, 2003, survey by CTPS, 21,142 vehicles traveled northbound in the four general-purpose lanes of I-93/Southeast Expressway between 6:00 AM and 10:00 AM, corresponding to an estimated 23,406 occupants—a ratio of 1.11 occupants per vehicle. That same morning, 4,193 vehicles traveled in the HOV lane, a volume that carried an estimated 12,451 occupants—a ratio of 2.97 occupants per vehicle.

HOV Lane Corridor Travel Time Observations
The travel time observations presented here are from the years 2002 and 2003. The 2002 data were collected before the opening of the northbound lanes of the Central Artery tunnel, which occurred in March of 2003, and 2003 data were collected after the tunnel opened.

The following three tables provide a summary of HOV-lane corridor operations in 2002 and 2003, organized by half-hour, hour, and full operation time periods. The summary accounts for both spring and fall data collection; these collection times generally correspond to the data collection periods for the CMS arterial roadways.

For I-93 North southbound traffic, the savings in travel time in the HOV lane seem to have improved between 2002 and 2003. The HOV travel times have not seemed to change, but the general-purpose lane travel times have increased.

The I-93/Southeast Expressway traffic seemed to remain more consistent between 2002 and 2003 than the I-93 North HOV lane traffic, in both the morning and evening peak directions. The observations show an improvement in travel-time savings of the HOV lane over the general-purpose lanes, particularly between the hours of 7:00 AM and 9:00 AM, for northbound traffic, and between 3:30 PM and 6:00 PM for traffic headed southbound from Boston.