While many shipping companies have had difficulty retaining a workforce of drivers, Walmart has invested heavily in its own shipping infrastructure, avoiding a trucker shortage.

Unlike many major retailers, Walmart maintains its own private fleet of 9,000 truck drivers, and the median salary for Walmart truckers is double that of the national median.

Ken Braunbach, Walmart's vice president of transportation, discussed the retailer's supply chain at Business Insider's IGNITION: Transportation event in San Francisco.

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Walmart's investment in its own trucking and supply-chain operations goes further than many of its competitors — and as a result, the retailer doesn't have a problem retaining truck drivers, according to Ken Braunbach, Walmart's vice president of transportation.

For years, trucking companies have warned about an ostensible truck-driver shortage in the US, with the American Trucking Association claiming that the US is short 50,000 truck drivers.

However, the Bureau of Labor Statistics and truck drivers themselves have said that no such shortage exists — rather, there's a lack of truckers willing to work 70-hour weeks for the low wages offered by most shipping companies.

Walmart's model seems to prove this theory. The company's median salary for its fleet of 9,000 truckers is nearly $90,000 per year, according to Braunbach, compared with the national median of roughly $42,000 per year.

"You pay a little bit more, but you get a more safe and loyal workforce," Braunbach said.

Braunbach spoke about Walmart's supply-chain practices during a conversation with the transportation reporter Rachel Premack during Business Insider's IGNITION: Transportation event in San Francisco on Tuesday.

During the event, Braunbach also weighed in on the impact of advancements in driver technology. Self-driving vehicles are still on the distant horizon for trucking, he said, adding that advancements in technology have largely helped make truck drivers' jobs easier so far.

He also reflected on how much Walmart has changed since he joined the company in 2002. Its biggest adaptation, Braunbach said, has been its shift in focus from expanding brick-and-mortar locations to investing in e-commerce. Shoppers have rapidly moved online for retail purchases, he said, adding "that speed in the last three to five years has been remarkable."