The number of freight trains traveling between China and Europe hit record levels, data from China's rail operator showed on Saturday, signaling growing economic ties between China and economies participating in theBelt and Road(B&R) initiative where the trains are purring along.

Nevertheless, market observers still call for sober minds to address concerns over the actual benefits of the rail routes for B&R economies that have yet to make full use of the trains to ship their products into the booming Chinese market.

The number of the trains hit a new annual record this year after initially being put into operation in 2011, according to the Xinhua News Agency, citing China Railway Corporation (CRC).

This year, over 3,000 freight trains have traveled on 57 lines from China to European cities, topping the combined numbers reached in 2011-16 and pushing the aggregate to more than 6,000, per the CRC data.

The cargo service, considered a significant component of the B&R, now serves as a bridge between 35 Chinese cities and 34 cities in 12 European countries.

The freight rail routes help cut logistics costs and improve trade efficiency between China and Europe - its largest trading partner - and more importantly serve to prove the viability of the B&R initiative as an enabler of trade connectivity, experts said.

In the first 10 months of the year, trade between China and Europe denominated in the Chinese currency grew 16.2 percent year-on-year, according to Chinese customs data.

There are other projects such as the yet-to-be-finished transcontinental expressway linking Lianyungang in East China's Jiangsu Province and St. Petersburg in Russia that are envisioned to build closer economic ties between China and B&R countries.

China has been making particular headway to create a more efficient transport network. The Chinese section of the transcontinental expressway recently opened to traffic.

But along with applause for the growing trade connectivity have come concerns that the cargo trains and expressways might aggravate imbalances of trade between China and some B&R economies.

The volume of cargo is still unbalanced with still a significant number of China-bound cargo trains carrying empty or partially loaded containers on the return journey, observers pointed out.

Ma Bin, an assistant researcher at the Center for Russia and Central Asia Studies, Fudan University, told the Global Times that to address bottlenecks for the development of China-Europe railway service, resources and networks need to be optimized to save costs and achieve efficiency.

"It is particularly urgent to create domestic distribution centers and regional ones along the route to coordinate the flow of goods,"

Since the Harbin-Europe line was launched in June 2015, now there are four lines from Harbin to European cities, with 642 trains carrying a total of 37,268 containers.

Among the trains, 311 were Europe bound and 331 China bound, according to Yan Hong, deputy general manager of Hao International Logistics Co, which operates a direct train between Harbin, capital of Northeast China's Heilongjiang Province and several European cities .

Europe bound trains mostly carry vehicles and components, machinery, electronics and daily necessities. China bound trains mostly carry autos and components and paper pulp, Yan told the Global Times on Sunday.

A total of 264 cargo trains have traveled through the Yixin'ou cargo line, carrying 21,536 containers by the end of October, Yixin'ou (Yiwu-Xinjiang-Madrid) service line said in a statement sent to the Global Times.

Yan noted that the biggest challenge facing the China-Europe railway service is high transportation cost as well as vicious competition among different lines.

Furthermore, as Ma put it, to strike a balance of cargo flows between China and Europe is not the only benchmark to assess the success of the China-Europe railway service. To achieve long-term sustainable development of the China-Europe express service, a transnational coordination platform should be established to optimize efficiency of the services and bond countries and regions along the route and allow them to share the mutual benefits, he suggested.

Chen Qingqing contributed to this story