Smooth vehicular ride-ability on repaved and new construction roadways is increasingly becoming a prime importance for many states' departments of transportation (DOTs). To achieve consistently smoother roadways, many DOTs are specifying the use of a material transfer vehicle (MTV).
One reason for specifying the inclusion of an MTV in the paving train is that hot mix asphalt (HMA) delivery trucks are never in contact with the paver since the MTV supplies the paver by its non-connecting conveyor. This eliminates dump trucks bumping the paver as they are backed into place for unloading the HMA into the hopper. If an MTV is not used, the truck bumping into the paver transfers a shock to the paving process, thus causing a slight bump in the pavement.
There are other reasons why the DOTs are specifying the use of MTVs. For example, the temperature of HMA delivered in a truck can lead to its cooling at the outer box areas, including at the open top and the sides of the truck's dump box. Aggregate segregation is another problem experienced. Segregation can take place during delivering the HMA and dumping of the load.
Both uneven temperatures and segregation in the HMA will lead to substandard pavement quality. The compacted densities of the pavement will vary and the binding properties will be compromised, resulting in less than acceptable smoothness.
Both the uneven temperatures and segregation problems are virtually eliminated with the use of an MTV, like the Roadtec Shuttle Buggy. It remixes the HMA immediately before it's released to the conveyor for loading the paver's hopper, thus ensuring a uniform temperature and the even redistribution of the aggregates.
Each DOT has its own wording for specifying the use of an MTV. For example, here is the Nevada DOT version as specified under section 401.03.03 Pavers:
"Use a Roadtec or approved equal self-propelled material transfer vehicle capable of remixing the bituminous material to prevent segregation and providing storage while maintaining consistent mix temperatures and transferring into the paver."
No MTV in your fleet?
Who is not for smooth roadways? The question is rhetorical, of course. Nevertheless, having to include an MTV into the paving train can be problematic for paving contractors who don't own one but want to do business with the DOTs. An MTV represents a major capital investment, so the contractor must have enough use for it to warrant the investment.
The good news is the investment often can be justified. Pat Hawbaker, paving operations manager for Glenn O. Hawbaker Inc., State College, PA, says the use of their Roadtec Shuttle Buggies has increased paving productivity by 25 to 30 percent. Hawbaker owns four of the units. The company employs 1,000 people with 200 of them in the paving division. In 2004, the company paved one-million tons of HMA on both public and private paving projects.
Hawbaker enjoys a high utilization rate for the Roadtec Shuttle Buggies during the paving season. However, the paving season in this area of Pennsylvania is about eight months since such activities are closed during the winter months.
"We use our Shuttle Buggies as much as is practical and we certainly use them on all the PennDot projects because its use is specified," he says. "Besides producing smoother pavements by using the Shuttle Buggies, we get higher paving productivity, which enables us to complete the paving projects much faster and more competitively."
MTVs are a sizable investment costing as much as $350,000. Hawbaker says the increased paving production can justify the cost. The secret is in keeping the machine busy.
"To keep our Shuttle Buggies busy year round, for the last six years we've been renting them," he explains. "We often rent them to contractors in Florida or Texas who pave year round. The results from this rental business have been very good. One way we reach the marketplace is through ads in trade publications."
It's a win-win proposition for Hawbaker and the contractors renting the equipment. Hawbaker gains by increasing the utilization of the Shuttle Buggies. Contractors gain paving contracts specifying the use of an MTV that would not otherwise be available to them.
Roadtec does not directly rent its equipment to contractors. That is a plus because many paving contractors, such as Hawbaker, can justify the investment in a Shuttle Buggy with the idea of renting to others when they themselves do not need it. "We bought this fourth Shuttle Buggy based on the fact that when we need it for a project it is there, and when we don't need it, we rent it to others. This is good for Roadtec sales, because contractors such as ourselves don't hesitate to buy more units knowing we're not depending solely on our own work. Roadtec even refers contractors to us who want to rent a unit," says Hawbaker.
Here are some guidelines for both the renter and one renting a MTV, as suggested by Hawbaker. For those owning an MTV, insist on including your own operator in the rental deal. Why? Because of safety issues. As is with any other equipment, the operator should be well trained and experienced to operate it. Hawbaker's operators are re-certified each year through a formal training program carried out by Roadtec instructors. Further, each operator has a two-way radio, as does the paver operator and the delivery truck supervisor, so they are in constant communications with one another. This communications network can avoid many potential mishaps.
Besides supplying the two-way radios to the renting contractor, Hawbaker emphasizes that his operators go over a litany of safety rules with the paving crew so everyone is fully informed on what MTV practices are acceptable and ones that are not. "If a contractor will not subscribe to our basic safety rules and procedures, we have instructed our operators to pull the Shuttle Buggy off the job and park it until management from both companies can settle our differences," says Hawbaker.
For the rental to be successful, it must be mutually beneficial, says Hawbaker. He says the contractor renting the MTV should be sure it is in top working condition and that the operator being supplied is experienced. "Roadtec Shuttle Buggies are known for their reliability if they are well-maintained and driven by skilled operators. Our oldest buggy has been used for seven years and it still is very reliable, with no major breakdowns experienced."
If an MTV breaks down, the paving process comes to a halt. Any equipment can and does fail at times. The contractor should make certain that the contractor providing the MTV will also provide just-in-time service. "We immediately dispatch our own mechanics for MTVs being rented in Pennsylvania and the neighboring states. Distant states are effectively covered by local Roadtec service mechanics. Besides good service, Roadtec delivers parts in a timely fashion," says Hawbaker.
An economical, quality approach
Mobilizing most MTV types is not problematical. Hawbaker has the Shuttle Buggies shipped by commercial carriers who specialize in transporting such equipment. Fortunately, a Shuttle Buggy weighs less than 80,000 lbs.
Not all contractors who rent buggies do so because their use is specified by the owner. It can be for economic and quality control reasons. For example, Trap Rock Industries Inc., Kingston, NJ has just paved a 4,800-foot long by 150-foot wide landing strip and 10 300-foot by 100-foot taxiways at the Trenton-Mercer Airport. Thirty-thousand tons of HMA were laid using two Shuttle Buggies in dual paving trains. One of the Shuttle Buggies is owned by Trap Rock, while the other is on rent from Hawbaker.
The paving production averaged 4,500 tons per nine-hour day. Jerry Shirey, paving supervisor for Trap Rock, says if the Shuttle Buggies were not used, the paving production would have been only 3,800 tons per nine hours. The key to higher production on this project was the continuous paving afforded by the MTVs.
Besides increased production, the use of MTVs ensured an outstanding smooth pavement on the landing strip. "We wanted the smoothest landing strip possible and the only way to be sure was to use the MTVs. It sure paid off," says Shirey.
Here is how Shirey set up the paving configuration to get both good production and pavement smoothness. Forty-four tandem and tri-axel dump trucks were required to keep paving continuously. At the fore of the train was the Shuttle Buggy followed by a Caterpillar paver. Next, each paving train included two new Ingersoll-Rand DD118 HF vibratory compactors for breakdown followed by two DD90HF vibratory compactors for intermediate compaction. Lastly, there was DD110 vibratory compactor used in the static mode for finishing.
Shirey says his company is considering purchasing two new Roadtec Stealth pavers to replace the old pavers. If this is done, the company will either rent a second Shuttle Buggy from Hawbaker or purchase one to round out the paving trains.
Contractors not owning an MTV should consider bidding on projects requiring one if the work looks profitable. Prior to bidding, however, it is prudent for them to contact Roadtec for the name of a qualified contractor who rents Shuttle Buggies such as Hawbaker. That way, they are assured of having one available for carrying out the project.