Port congestion in China and Brazil as well as Australia has tied up large numbers of capesize and smaller panamax vessels this year, meaning there is a smaller number of available ships which has helped to buoy freight rates.
Capesize ships typically haul 150,000 tonne cargoes such as iron ore and coal, while panamaxes are also used to ferry coal. One of the main choke points has been in ports on Australia's east coast, including Dalrymple Bay and Newcastle.
Shipbroker SSY estimated the average waiting time at seven of the largest Australian coal ports on its east coast had risen to 13 to 14 days from six to seven days in April.
"The congestion issue is supportive of freight as it cuts fleet supply," Derek Langston, a director with SSY Consultancy and Research, said.
Shipping analysts expect countries such as China and India to step up their coal imports in the coming years even as infrastructural investment at ports lags behind.
"The medium-term outlook is for strong coal prices because of inadequate supply and increased demand which stems from China and India," Will Fray, shipping analyst with London-based consultants Maritime Strategies International, said.
"In shipping terms, there is going to be a huge amount of demand and that will ramp up congestion at ports particularly on short-term cycles and that could be a real driver behind quite volatile freight rates."
While Chinese appetite for iron ore - the primary material in the manufacture of steel - has dominated freight activity this year, some analysts expect demand for coal to play a bigger role for the shipping sector in the coming years.
With electricity demand surging in Asia, utilities are seeking coal from much further afield than ever before, such as the United States and South Africa, to avoid costly port delays, shipping analysts and coal buyers said.
"We see coal as the next big driver for the (freight) market," Georgi Slavov, head of dry freight research and structured products at ICAP Shipping, said.
Shippers hope that as demand for vessels grows, and so does port congestion, it will help alleviate the problem of oversupply in the seaborne sector, which is set to gather pace next year and hurt freight rates.
"The increasing tonnage supply will somehow be absorbed on the way which means a better freight market," ICAP's Slavov said.
Clogged rail links from coal mines to ports in major exporters Russia, South Africa and Australia are failing to cope with the volume of traffic and this will help send coal prices sharply higher next year.
In Australia and elsewhere, severe congestion in ports is also tying up a large number of ships used to carry coal, driving freight rates up and making them volatile.
"Next year, as soon as we see trading intensity increasing, you will have more queues and both freight and coal prices will rise," Societe Generale analyst Emmanuel Fages said.
As the world economy rebounds in 2010, coal producers and users expect the volume of coal traded to increase. Strong coal demand in Asia, led by China and India, will push European delivered coal prices up to $100 a tonne by June from $70 now, according to Bank of America Merrill Lynch.