New Tier 4 generation engines and equipment will require the use of ultra-low sulfur diesel fuel, which has no more than 15 ppm sulfur, according to the Diesel Technology Forum. This fuel has been used since 2006 in on-highway vehicles.

“Older off-road machines and engines can continue to use the higher sulfur fuels, which will be available in diminishing quantities nationwide until December 2011,” the forum says. “Supplies of the old ‘higher sulfur’ diesel fuel will be diminishing rapidly beyond 2010, but still may be available in some more remote locations and areas of the country.”

What is on the horizon? Now that Tier 4 diesel emissions are near zero, under the Obama administration EPA may set its sights on carbon dioxide emissions, which are thought to advance presumed global warming. Thus, the regulators may be able to continue their career mission: issuing regulations. In the meantime, off-road Tier 4 engines will become a reality in 2011.

For more information, visit the Diesel Technology Forum at www.dieselforum.org or visit the Clean Diesel Fuel Alliance at www.clean-diesel.org.

Future Performance of Raised Markers

The Texas Department of Transportation (TxDOT) is looking to recent research to indicate performance of retro-reflective raised pavement markers in 2011 and beyond, it was reported late this year.

Precast concrete pavement slab is lowered into Utah’s I-15 between Clearfield and Layton.

As a Sunbelt state, Texas can take advantage of retro-reflective raised pavement markers (RRPMs) to guide motorists on dark and rainy nights (snow plows tend to bust RRPMs off a pavement). Their durability and performance are of critical importance to the agency. But recently TxDOT began to notice an increased number of RRPM failures such as poor retention on pavements, physical damage and loss of retro-reflectivity.

In response, the Texas Transportation Institute (TTI) began to research the causes of premature RRPM failures. “All the markers that TxDOT was using met the requirements set by ASTM specifications,” said Yunlong Zhang, TTI assistant research scientist and research supervisor, earlier this year. “However, RRPM performance varied significantly, and the results from existing testing methods also did not correlate with field performance.”

Damage to shell of retro-refective raised pavement marker could be caused by something as simple as a stone wedged in tire tread.

TTI was asked to identify or develop new lab testing methods that would help the state more accurately predict marker performance in the field. Over a three-year period, researchers conducted multiple tasks that included lab and field tests, as well as surveying TxDOT districts and RRPM manufacturers to gather information on existing test procedures and marker field performance.

The researchers monitored four test deck locations selected according to traffic condition and pavement type. “For example, one of our test decks was on the I-610 Loop in Houston, which is a very high-volume concrete roadway,” Zhang says. “We also had a test deck on a low-volume road with a flexible pavement surface. The goal was to get a wide range of test data in different scenarios.”

The research yielded several important findings with respect to RRPM future performance and testing methods: