Automated Inspection of Concrete Crossties Mandated
In a final rule taking effect July 1, the Federal Railroad Administration requires computerized inspections, saying they are better than visual inspections at finding weak points.
A final rule from the Federal Railroad Administration requires automated inspections of concrete crossties beginning July 1, 2011. FRA said visual inspections do not analyze weak points in track geometry and structural components as well as computerized inspections.
The rule also adjusts requirements for concrete crossties and for rail fastening systems connected to them.
An Amtrak train's derailment at 60 mph on April 3, 2005, on curved track running through the Columbia River Gorge in Washington state is the impetus for the rule. The derailment occurred on a 3-degree curved, according to the rule, injured 30 people, and resulted in $854,000 of property damage. NTSB conclude a cause was excessive abrasion of concrete crossties, which allowed the outer rail to rotate outward and create a wider gage track condition. "This accident illustrated the potential for track failure with subsequent derailment under conditions that might not be readily evident in a normal visual track inspection," FRA said in the rule. "Conditions giving rise to this risk may include concrete tie rail seat abrasion, track curvature, and operation of trains through curves at speeds leading to unbalance (which is more typical of passenger operations). Subsequently, this accident also called attention to the need for clearer and more appropriate requirements for concrete ties, in general. This final rule addresses this complex set of issues."
Crossties once consisted solely of wood, but FRA says the first use of concrete ones was in 1893. Improved continuous welded rail processes, elastic fastener technology, and concrete prestressing techniques has increased the use of concrete crossties. They transmit wheel loads better than traditional wood crossties and are not much affected by temperature changes, but they are susceptible to stress from high-impact loads. Concrete crossties now account for about 20 percent of the crossties installed by major U.S. railroads, the rule states.