Congestion levels and trends are another important indicator of highway funding needs. As with road pavement conditions, MDOT, Anderson Economic Group, and TRIP all have recent reports on the issue. In addition, SEMCOG has reported on congestion levels in Southeast Michigan.
MDOT has defined “congested” roads as those with a Level of Service (LOS) of “F” for freeways and “E” or “F” for none-freeways. LOS is determined using the guidelines in the Transportation Research Board’s Highway Capacity Manual 2000. Table 8 summarizes changes in congestion levels over time assuming no capacity is added in additional lane miles. MDOT’s analysis suggests that 15.3 percent of urban freeway VMT in the state was congested in 2004, with 39.9 percent of the urban freeway VMT approaching congestion status. Urban non-freeway trunkline VMT was 20 percent congested, with 22.8 percent of VMT approaching congested. Under current funding, the level of congested VMT on urban freeways will increase to 42.6 percent by 2030, with 39 percent of nonfreeway urban VMT congested by 2030. For commercial vehicle miles traveled (CVMT), on freeways the congestion levels were at 9.5 percent in 2004, and reach 32.2 percent by 2030. For non-freeways 17.6 percent of CVMT was congested in 2004, with 36.2 percent by 2030. These congestion levels are unacceptable even by 2015, and will be unbearable by 2030. In order to avoid the 2015 congestion levels additional investment will be needed.
SEMCOG has also analyzed current and likely future congestion in Southeast Michigan. By 2030, if no capacity is added, there will be 96 miles of “bottleneck” (less than one-half mile) roads in southeast Michigan, and over 1400 miles congested. They estimate these congestion levels will impose a cost of $3.96 billion by 2030.
Anderson Economic Group also has analyzed statewide congestion levels in comparison to other states. Anderson uses FHWA Highway Statistics data from Table HM-61 for this analysis. This table reports the Volume Service Ratio (VSR) for roads and assumes that roads with a VSR above .80 are congested. The higher the ratio the worse the congestion. For 2005, Michigan’s urban interstates were 43.8 percent congested, compared to a Midwestern state average of 40.5 percent, and a U.S. average of 32.6 percent. Ohio’s urban interstates are more congested than Michigan’s, and Illinois has similar levels of congestion. For urban, non-interstate freeways, Michigan congestion miles equal 29.6 percent, with Midwestern states averaging 19.4 percent, and the U.S. average at 19.5 percent. Ohio was at just 8.9 percent, and Illinois at 14.3 percent. For other principal arterials 14.6 percent of Michigan miles are congested, as compared to the national average of 10.9 percent. Similar Ohio roads are just 5.6 percent congested, and Illinois ones are 7.0 percent congested. What this indicates is that Michigan urban roads are more congested than neighboring states, the Midwestern state average, and the national average.
Anderson also reports on data from the Texas Transportation Institute’s 2005 Urban Mobility Report. This data shows that Detroit has a travel time index (ratio of peak traffic flow times to free flow travel times) of 138 percent, meaning it takes 38 percent longer to make a trip at peak traffic times than it does at non-peak times. Detroit ranks 17th among large urban markets on this measure. By comparison, Chicago had a ratio of 158 percent, and the average ratio for 85 areas measured was 137 percent. Separate data from the Texas Transportation Institute, summarized in a Detroit News editorial in 2005, indicates that Detroit motorists spend 119 million hours/year in delays, and burn an extra 72 million gallons of fuel per year, with $2 billion in lost time costs per year.
TRIP also reports on congestion levels in Michigan, but reports percent of miles congested rather than percent of VMT as MDOT does. The MDOT approach does not show as great a level of congestion and would seem to be more reliable an indicator of the level of congestion. Using their approach, TRIP reports that 36 percent of urban interstate miles were congested in 2004. They also indicate that travel on Michigan interstates grew by 33 percent between 1990 and 2004 while lane miles increased by just 3 percent. TRIP forecasts that travel on Michigan urban interstates will grow 40 percent by 2026, and that absent lane additions 63 percent of miles will be considered congested at that time.