A new report has accused transportation companies of lagging behind other sectors when it comes to greening their act.

The report, from a global study conducted by the non-profit Carbon Disclosure Project (CDP), said that transport could have a "major long-term impact on climate change" if strategic investments are not made.

Analysts surveyed 291 of the largest transport companies in the world said that only 36 percent of them have set carbon and energy targets, compared to 51 percent of the "Global 500 Index" of companies across all sectors.

The CDP, which claims that its study is the first of its kind in the transportation industry, looked at firms including airlines, automakers, train operators, car rental firms and freight companies and found those based in South America were the most likely to have set reduction targets.

Sixty percent of South American firms had set targets to reduce their emissions, followed by 52 percent of European firms, 47 percent of North American firms, 30 percent of firms from Australia and New Zealand and only 18 percent of Asian firms.

The researchers singled out Air France-KLM, EasyJet, Canadian National Railways, Toyota, and UPS as among the minority of companies reporting significant investments.

“As the first real glimpse into the transport sector’s impact on climate change, I’m pleased to see that there are some clear leaders making good progress in setting targets and making investments in low-carbon alternatives," said CDP's Zoe Tcholak-Antitch.

"The overwhelming conclusion, however, is that the sector as a whole needs to transform and realize the opportunity to make a profound impact on the environment and the business benefits to reducing emissions."

The areas where cuts need to be made could not have been more clearer - road transportation accounts for a whopping 80 percent of the sector's total CO2 contribution, followed by air (13 percent) and sea transportation (7 percent).