Putting Tugs and Carts to Work in Your Warehouse
Need to optimize the flow of freight inside your distribution center? A tug-and-cart system might be the answer.
Next time you find yourself sitting on an airplane, waiting to push back from the gate or taxiing across the tarmac toward takeoff, take a minute to study those tugs pulling baggage carts as they worm their way to and from the airport terminal.
Imagine how much time, manpower and equipment it would take to move all of that “freight” between the planes and the terminal’s conveyors and carousels if the baggage were being transported just one or two pieces at a time. Sounds pretty inefficient, right?
But that’s exactly the scenario playing out inside many distribution centers every business day. Forklifts loaded with one or maybe two stacked pallets of finished product or material move from a receiving dock into inventory, or from inventory to staging, and eventually on to shipping and loading. Especially in a high-volume operation, this back-and-forth, onesie-twosie movement of freight gets repeated dozens, even hundreds, of times daily.
Having forklifts and their operators in constant, to-and-fro motion might appear, on the surface, to be the hallmark of a productive, high-velocity distribution center (DC). But in fact, it could be the sign of inefficiency in the operation, where both time and labor are being wasted.
The good news? It’s a source of time and cost inefficiency that can be fixed by taking a cue from airline baggage handling.
Taking a Tug-and-Cart Approach
A few years ago one of Landair’s customers faced the scenario described above inside one of its DCs. Pallets containing finished product (in this case, a relatively heavy piece of motorized equipment) would arrive from the factory, be scanned into inventory and then get transported via forklift to designated holding areas that were “mirrored,” or replicated, throughout the DC.
Because this particular product sold in high quantities during peak seasons, heavy volumes of orders would later require that multiple forklifts make dozens of trips each day to move finished product — stacked two pallets high — out of inventory to a shipment-processing staging area. Even though inventory was mirrored at various locations (so some round-trips were shorter than others), it took multiple forklift operators up to 18 minutes to move 16 pallets of finished product from inventory to shipment staging.
When this customer recognized that its tried-and-true approach to order picking and flow was not keeping pace with demand, they approached Landair looking for a better, higher-velocity strategy. As we studied the process we noted that velocity could be increased dramatically if each forklift were able to carry more than two pallets per trip. But the customer would still have the inefficiency that comes with forklifts spending as much as half of their operating time moving empty. Plus, stacking more than two pallets vertically was not an option. So, we decided to come at the problem horizontally.
In other words, we determined that by borrowing the tug-and-cart strategy used by airline baggage handlers, we could move 16 pallets of finished product from inventory to staging in as little as seven minutes. Implementing the strategy required purchasing and custom-configuring a small fleet of carts to accommodate the customer’s pallets. The carts were designed to be ganged into trains and pulled by either a forklift, an actual baggage-handling tug, or even a lawn-and-garden tractor.
The tug-and-cart system brought immediate order and efficiency to what had been an inefficient (and, the customer would admit, somewhat chaotic) process involving as many as a half dozen warehouse employees and forklifts. Now one forklift operator could focus on inventory picking and cart loading. Another concentrated on unloading the carts at staging. A third drove the tug. Fewer employees and forklifts were needed to accomplish more-productive work. And the forklifts being used spent relatively little time moving empty. Overall, the customer realized savings of $98,000 annually, primarily through a reduction in head count.
I’ve seen a tug-and-cart system used successfully by a food company that processes canned vegetables; the nature of their business requires large volumes of product moving at high velocity during peak harvest and packaging seasons.
But this approach to transportation inside DCs isn’t limited to businesses that have seasonal demand spikes. Almost any warehouse operation where significant amounts of time, equipment and labor are spent moving inbound goods into inventory, and then picking and moving orders to staging and shipping, could potentially benefit from a tug-and-cart strategy.
In fact, the larger your DCs are, the more likely you’re expending time and resources having forklift operators making multiple trips over considerable distances (resulting in significant unproductive time for the forklift and driver). For many organizations, a tug-and-cart system could also represent a substantial improvement in workplace safety, compared with multiple forklifts traveling long distances at high speeds in order to keep up with fulfillment demand.
Modeling a Tug-and-Wagon System
A distribution management consultant or 3PL should be able to help you with process- and cost-modeling to determine whether a tug-and-cart system will create efficiencies and return on investment for your business. Among the variables they’ll want to weigh are:
- • Physical size and configuration of your DC, along with your established processes and business requirements for inbound freight, inventory/storage, order picking and shipment staging/processing.
- • Time, staff and equipment benchmarks for moving X volume of product or material to its intended destination (e.g., an inventory bin or rack, the shipping area).
- • Amount of your product that can be loaded and moved safely and securely on a train of connected carts.
- • Any capital investment that might be required to add a fleet of carts, and perhaps even an actual luggage tug, to your operation.
- • Equipment or personnel that could be eliminated, or redeployed to more productive activities.
Like so many distribution management challenges, the tug-and-cart strategy boils down to exploring better ways to optimize throughput — moving more product with less labor, in less time, at a reduced or comparable cost.
In this case, it’s a velocity-improvement strategy that borrows from the airlines. Only not from their 500-mph planes. Instead, from their slower-moving but still operationally effective baggage tugs and trains.
VP, Supply Chain Solutions
Jim Massengill’s career spans more than 25 years as an operations leader, consultant and executive manager for logistics and transportation organizations.