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

Southeast Expressway: Comparison of HOV and General-Purpose Lanes


Northbound
MPO staff developed historical travel time trends from the 2002 to 2011 monitoring years (see note below the graph) for the northbound Southeast Expressway HOV and general-purpose lanes. Travel times for both the HOV and general-purpose lanes were shortest in 2002 and have been increasing since then, as shown in the graph below. However, the HOV lane is becoming more attractive, as the travel times in the general-purpose lanes have been increasing at a faster rate than travel times in the HOV lane, resulting in increased travel-time savings for the HOV lane. The gradual increase in travel times over the years for both the HOV and general-purpose lanes might be attributable to several factors influencing the operations of both. One possible factor is an increase in the volume of vehicles that use the HOV lane. Another possible factor is that the merge of HOV traffic with general-purpose traffic at the north end of the HOV lane may cause delay for both the general-purpose lanes and the HOV lane. Further study would be needed to determine the main causes of the increasing travel times.


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.

Travel times in both the HOV and the general-purpose lanes during each daily period of operation increase from 6:00 AM to a peak around 8:00 AM and then decrease until the end of HOV operations at 10:00 AM (as shown in the appendix of the memorandum available for download at right).

As shown in the table below, the HOV lane is more efficient than the general-purpose lanes, as it carries more persons per lane. During 2010, it carried an average of 1,008 vehicles per hour per lane during the four hours of operation and 1,400 vehicles during the peak hour. The number of persons per hour per lane carried by the HOV lane is more than twice that carried by the general-purpose lanes.

Southeast Expressway, Northbound 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		 Percent
Difference
in Persons
per Hour
per Lane*		 Persons
per
Vehicle
2005 HOV 3,898 10,769 975 2,692 – 2.76
General 22,688 25,367 1,418 1,585 – 1.12
All 26,586 36,135 1,329 1,807 70% 1.36
2006 HOV 4,156 10,954 1,039 2,738 – 2.64
General 18,237 19,215 1,140 1,201 – 1.05
All 22,393 29,937 1,120 1,497 128% 1.33
2007 HOV 4,468 12,012 1,117 3,003 – 2.69
General 20,534 22,018 1,283 1,376 – 1.07
All 25,002 34,030 1,250 1,701 118% 1.36
2008 HOV 3,559 9,855 890 2,464 – 2.77
General 21,044 22,751 1,313 1,422 – 1.08
All 24,563 32,606 1,228 1,630 173% 1.33
2009 HOV 3,925 10,630 981 2,658 – 2.71
General 21,779 23,515 1,361 1,470 – 1.08
All 25,704 34,145 1,285 1,707 181% 1.33
2010 HOV 4,030 11,455 1,008 2,864 – 2.84
General 19,383 21,169 1,211 1,323 – 1.09
All 23,413 32,623 1,171 1,631 216% 1.39
Note: Vehicle occupancy monitoring for the Southeast Expressway began
            in the fall of 2004 (monitoring year 2005).

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


Vehicle- occupancy counts are not conducted for the PM hours of operations on the Southeast Expressway (they are assumed to be similar to the occupancy counts in the AM hours).

Southbound
Average travel times for the Southeast Expressway southbound HOV lane have remained almost static over the years, increasing only by a very small amount from 2002 to 2010. Travel times for the general-purpose lanes increased from 2002 to 2008 (more gradually than for the northbound HOV lane), then decreased slightly from 2008 to 2010. This has caused an increase over the years in the amount of time saved by users of the HOV lane.


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).

The travel time curves over the years have been quite similar (see the memorandum available for download at right for more information). Travel times were higher in 2005 to 2008 than in 2003 to 2005 for the general-purpose lanes, but were lower again in 2009 and 2010. Again, there may be several reasons for these observations, including but not limited to the volume of vehicles that use the HOV lane as well as the merge of the HOV lane with the general-purpose lanes. Further study would be needed to identify the main causes. Travel times in both the HOV and the general-purpose lanes during each daily period of operation increase gradually from 3:00 PM to a maximum around 5:00 PM and then decrease until the end of HOV operations at 7:00 PM.

Vehicle-occupancy counts are not conducted for the PM hours of operations on the Southeast Expressway (they are assumed to be similar to the occupancy counts in the AM hours).

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