Interstate Bridge Conditions: Which Routes Have the Most Poor Bridges

Which Interstates have the highest share of Poor bridges

I-57 has the largest share of main-line bridges rated Poor among Interstates with at least 100 of them: 30 of 277, or 10.8 percent. That is about four times the 2.6 percent for every main-line Interstate bridge in the country. All 30 are in Illinois, which holds 265 of the route's bridges.

Four more routes are above 8 percent: I-82 at 10.1, I-79 at 9.0, I-83 at 8.9 and I-87 at 8.2. Each has between 101 and 366 bridges, so a handful of ratings moves them a long way. On I-82, which has 109, one more Poor bridge would add almost a full point.

Twenty-eight of the 58 ranked routes sit above the system figure. Eight have no Poor main-line bridges at all. Two of the longest routes rank near the bottom: I-10 carries more main-line bridges than any other Interstate, 3,060, and only 21 rate Poor (0.7 percent), while I-35 has 9 Poor bridges out of 1,866 (0.5 percent).

The share counts structures and nothing else. It is not weighted by traffic, length or deck area, so a short rural overpass counts the same as a long river crossing in a city.

I-90 carries the most Poor bridges of any Interstate

I-90 has 116 main-line bridges rated Poor, more than any other Interstate and 11.0 percent of the system total. Three states hold most of them. Washington has 40, and New York and Massachusetts have 23 each, for 86 of the 116.

Raw counts mostly track how many bridges a route has. I-80 (77 Poor), I-70 (67) and I-40 (63) come next, yet their shares are all within about a point of the 2.6 percent system figure. Together the ten routes in this table hold 571 Poor bridges, 54.1 percent of the 1,056.

Within a route, the Poor bridges often cluster in one state. On I-5, 46 of the 52 are in California, and on I-70, 30 of 67 are in Colorado. I-95 has 45 Poor bridges, but they are only 2.2 percent of its 2,044, below the system figure.

The worst state stretches, led by I-79 in West Virginia

Among route and state pairs with at least 50 main-line bridges, the worst is I-79 in West Virginia, where 33 of 168 main-line bridges rate Poor, or 19.6 percent. Those 33 are every Poor bridge on the route. Its 198 bridges in Pennsylvania include none.

I-84 in New York is second at 19.1 percent (18 of 94), and I-90 in Washington third at 16.3 percent (40 of 246). Both routes look very different elsewhere. I-84 has 1 Poor bridge among 206 in Oregon, and I-90 has 1 among 268 in South Dakota.

Illinois appears five times in the top 20, on I-70, I-80, I-57, I-94 and I-64. New York appears four times. The table needs at least 50 bridges in the state, so short pieces drop out: I-70's 23 bridges in West Virginia, 3 of them Poor, fall below that floor.

Older routes rate Poor more often, with exceptions

I-83 has the oldest main-line bridges of any Interstate with 100 or more: half were built in 1959 or earlier. I-76 follows with a median of 1960, then I-87 and I-96 at 1962. Thirty-two of the 58 ranked routes have a median year in the 1960s.

Age and condition move together, though loosely. Pooled, the 12 ranked routes with a median of 1965 or earlier have 3.7 percent of their bridges rated Poor. The 13 with a median of 1975 or later have 1.8 percent. Some routes break the pattern. I-44, with a median of 1964, has 1.3 percent Poor, half the system figure, while I-82, with a median of 1980, has the second highest share at 10.1 percent.

The youngest sets of bridges are on I-41 (median 2011), I-4 (2007) and I-99 (2001). The median uses the year built recorded for each bridge, so a later deck replacement or widening does not make a bridge count as newer.