A recent study of the 20 largest publicly traded freight transport and logistics companies has found that six of the firms had more debt on their books than the value of their net intangible assets, a sign that some companies that borrowed heavily to finance acquisitions in recent years are now paying a price for that strategy.

The study, conducted by U.K. consultancy Transport Intelligence, found that "intangible" assets—mostly made up of goodwill from acquisitions—accounted for one-quarter of the total $132 billion in assets held by the 20 companies surveyed. Six of the 20 have net indebtedness exceeding the value of their net tangible assets, according to the study. Net indebtedness is defined as the amount of borrowing net of a company's cash balances, the study said.

One of the six is Deutsche Post DHL, which is the world's biggest publicly traded logistics company and which has been one of the industry's most prolific purchasers of transportation assets over the past 15 years. Among its purchases have been express delivery giant DHL, freight forwarders Danzas and Air Express International Corp., and warehousing and logistics company Exel.

Transport Intelligence said although earnings reductions due to the economic downturn have reduced the book value of intangible assets held by the firms surveyed, the level remains uncomfortably high.

The industry needs to see an improvement in business "not only to justify the [$30.5 billion] of intangible assets that remain [on] the balance sheets but more immediately to service the borrowings taken on to acquire both goodwill that remains and also the goodwill that has been written off," said TI Senior Analyst David Bagshaw.