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Mobility Monitoring – HOV Lanes – I-93 North HOV Lane Trends
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Overview • I-93 North HOV Lane Trends • I-93 / Southeast Expressway HOV Lane Trends

I-93 North: Comparison of Southbound HOV and Southbound
General-Purpose Lanes


MPO staff developed historical travel time trends from the 2002 to 2010 monitoring years (see note below the graph) for the I-93 North HOV and general-purpose lanes, which show interesting characteristics. Travel times for both the HOV and general-purpose lanes were longest in 2002 and began decreasing as several milestones of the Central Artery/Tunnel project were accomplished, as shown in the graph below. The shortest average travel times were observed in 2007–08; since then, travel times in both the HOV and general-purpose lanes have been increasing slightly. Another trend is that the travel time difference between the HOV lane and general-purpose lanes steadily decreased between 2002 and 2006, then increased again from 2008 to 2010.


Note: The first season of a monitoring year is the fall of the previous calendar year, in accordance with the HOV monitoring program (for example, monitoring year 2004 begins in the fall of 2003). All references to a specific year on this page refer to the monitoring year, not the calendar year.

In the 2002 and 2003 monitoring years, travel times in the HOV lane during each daily period of operation rose gradually from 6:00 AM to a maximum around 8:00 AM and then decreased until the end of operations at 10:00 AM (as shown in the appendix of the memorandum available for download at right). However, from 2004 through 2010, the travel times in the HOV lane showed no peaking, as the congestion at the point where it merges with the general-purpose lanes was removed upon the opening of the Zakim Bridge and the southbound tunnel. In 2002 and 2003, travel times in the general-purpose lanes increased gradually from 6:00 AM to a maximum around 8:30 AM, and then decreased gradually until the end of the morning peak period for each year of observation. The travel times in the general-purpose lanes from 2004 through 2010 were significantly lower than those observed in 2002 and 2003, because the congestion at the point where the general-purpose lanes merge with the HOV lane was removed when the Zakim Bridge and the southbound tunnel opened. In addition, the peak travel time occurred later (between 9:00 and 9:30) in 2009 and 2010.

The HOV-lane volumes increased steadily from an average of 575 vehicles per hour per lane in 2004 to about 730 vehicles per hour per lane in 2010 (a 27 percent increase in six years), as shown in the table below. The volume of vehicles per hour per lane for the general-purpose lanes also increased, from 1,286 in 2004 to 1,708 in 2007 (a 33 percent increase in four years), but decreased to 1,383 in 2010. The increase in the HOV-lane volumes occurred despite the opening of the Leverett Circle connector in 1999, when access from the HOV lane to the Leverett Circle connector (serving Storrow Drive and points west) was eliminated. Because carpools, vanpools, and other vehicles heading to Leverett Circle can no longer take advantage of the HOV lane, more vehicles are using the general-purpose lanes and increasing those lanes´ person-carrying effectiveness. Still, the HOV lane is more efficient than the general-purpose lanes, as it carries more persons per hour per lane.

I-93 North, Southbound Vehicle Occupancy
6:00 AM to 10:00 AM
Monitoring
Year		 Facility Total Vehicles Total Persons Vehicles
per Hour
per Lane		 Persons
per Hour
per Lane		 HOV
Lane
Efficiency
Rate*		 Persons
per
Vehicle
2004 HOV 2,300 7,015 575 1,754 – 3.05
General 10,291 11,556 1,286 1,445 – 1.12
All 12,591 18,571 1,049 1,548 121% 1.48
2005 HOV 2,669 8,017 667 2,004 – 3.00
General 11,746 12,888 1,468 1,611 – 1.10
All 14,415 20,905 1,201 1,742 124% 1.45
2006 HOV 2,820 8,022 705 2,005 – 2.85
General 13,007 14,568 1,626 1,821 – 1.12
All 15,827 22,589 1,319 1,882 110% 1.43
2007 HOV 2,986 8,389 747 2,097 – 2.81
General 13,663 15,540 1,708 1,942 – 1.14
All 16,649 23,929 1,387 1,994 114% 1.44
2008 HOV 3,090 8,545 772 2,136 – 2.77
General 13,512 15,164 1,689 1,896 – 1.12
All 16,602 23,709 1,383 1,976 113% 1.43
2009 HOV 2,982 8,347 745 2,087 – 2.8
General 12,980 14,062 1,623 1,758 – 1.08
All 15,962 22,409 1,330 1,867 119% 1.4
2010 HOV 2,920 7,599 730 1,900 – 2.6
General 11,066 12,403 1,383 1,550 – 1.12
All 13,986 20,002 1,166 1,667 123% 1.43
Note:  Vehicle occupancy monitoring for I-93 North began in the fall of 2003
            (monitoring year 2004).

* HOV lane efficiency rate = Persons per hour per HOV lane divided by persons
    per hour per general-purpose lane, multiplied by 100.


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