Transportation System Performance-Arterial Speeds

ARTERIAL ROADWAYS:
Average Peak-Period Travel Speeds

The discussion below refers to the tables Summary of Average Observed Travel Speeds: Arterial Roadways, 2001–2003 and Summary of Speed Index: Arterial Roadways, 2001–2003.

(Click here for Average Peak-Period Delays at Intersections on Arterial Roadways) Arterial Roadways

Overall, about 9 percent of the monitored Class III (arterial) roadway miles in the region experience average travel speeds of 18 mph or less in the morning peak period. This number increases to 12 percent in the evening peak period. About one-half of these slow-travel miles are on the monitored roadways located in the Boston and inner suburbs subregion.

The difference in travel speeds between roadways in the Boston and inner suburbs subregion and roadways in the outer suburbs is strongly apparent. In the morning peak period, 20 percent of the monitored arterial roadways in the Boston and inner suburbs subregion have travel speeds of 18 mph or less, compared to 5 percent in the outer suburbs subregion.

In the evening peak period, 28 percent of the monitored arterial roadways in the Boston and inner suburbs subregion have travel speeds of 18 mph or less, compared to 8 percent in the outer suburbs subregion. Furthermore, only a quarter of the arterial roadways in the Boston and inner suburbs subregion have average speeds above 30 mph in the evening, compared to nearly 70 percent for the roadways in the outer suburbs.

Percent of Class III Arterial Roadway Miles by LOS Category, Morning Peak Period

Percent of Class III Arterial Roadway Miles by LOS Category, Evening Peak Period

Regionwide, about 16 percent of the monitored Class III arterial roadways have average observed speeds that are less than 70 percent of the speed limit for the morning peak period; in the evening peak period, this figure is 19 percent. In terms of average observed speeds near or above the posted speed limit, 62 percent of the roadways in the morning peak period were observed in this range; in the evening, this number drops to 55 percent. Of the CMS roadways in the Boston and inner suburbs subregion, slightly less than a third had observed average speeds in the evening peak period near or above the posted speed limit.

The Class III roadways in Boston and its inner suburbs show a great difference in the speed index between the morning and evening peak periods: 31 percent of roadways in the morning have average observed speeds that are less than 70 percent of the speed limit, as compared to about 40 percent of roadways in evening period.

Major Arterial Roadways
Traffic on 13 percent of Class I/II (major arterial) roadways have travel speeds of 27 mph or less during the morning peak period, worsening to nearly 18 percent during the evening peak period.

For Class I/II arterial roadways, the speed index between the morning and the evening peak periods shows a different congestion picture. Fewer of these major arterials with some limited access have average observed speeds that are less than 70 percent of the posted speed limit in the evening peak period: 21 percent, compared to nearly 25 percent of these roadways in the morning peak period.