Letter (b) may be described as civil or marine "blocking and trapping" cover. Such cover was developed in war risk policies both to provide total loss compensation if the vessel was blocked or trapped for an extended period (12 months usually) and to compensate loss of income during the period the vessel was delayed, see Cl. 15-12 and Cl. 15-16. On the latter provision, see under 16.1 below.
The blocking and trapping cover under Cl. 16-1, sub-clause 2 (b), is narrower than the cover under Cl.15-16. Only delays caused by physical obstructions are covered. Such obstructions may be another vessel blocking the entrance to the port after an accident, a collapsed bridge, fallen power lines, etc. The only obstruction excluded is ice. Delay caused by ice preventing the vessel from leaving the port is not covered. However, if ice was only one contributing cause of the delay, there may be partial cover if the other cause is covered under the loss of hire insurance, see further on causation under 3.2 above.
After the Deepsea Horizen catastrophe in the Gulf of Mexico, ports were temporarily closed due to extensive oil pollution in the port. Whether extensive pollution on the sea amounts to a “physical obstruction” is debateable. Oil on the sea will not physically prevent vessels from passing through, but if the port authorities in the port affected by the pollution do not prohibit vessels from passing through, port authorities at the next and subsequent destinations may well deny a vessel stained by oil entrance because of fear of pollution. Hence, the vessels that have to wait in port until the pollution is cleaned up are for practical and commercial reasons blocked. Thus, there are good reasons to treat extensive pollution equal to a physical obstruction in relation to Cl. 16-1, sub-clause 2 (b).
If the vessel is prevented from entering (as opposed to leaving) a port because the entrance is blocked, the ensuing delay, loss of freight or extra costs of discharging or loading the cargo elsewhere, is not covered under the loss of hire insurance. The market at this point of time is still not prepared to extend cover any further than to vessels blocked in port or similar limited areas. A vessel prevented from entering a port may, of course, move freely in the physical sense, but from a legal standpoint its movements may be restricted because of its contractual obligations which may oblige the assured to keep the vessel waiting for a certain period to see whether the hindrance disappears and prevents him from taking any action to mitigate the loss until after a considerable time. Thus there is no doubt that if the vessel cannot enter a port because of a physical obstruction, the assured may suffer losses worthy of being covered by loss of hire insurance but which losses are nevertheless uninsurable under the generally available loss of hire insurance conditions.
The words "similar limited area" are not commented on in the Commentary to Cl. 16-1, sub-clause 2 (b), other than by reference to Cl. 15-12 (war risk blocking and tapping). In 16.1 below, it is explained that the whole Arabian Gulf is deemed a "similar limited area" to a port or harbour for the purpose of Clauses 15-12 and 15-16 and it is suggested, in opposition to the Commentary that the same may apply to other gulfs and bays etc. The same extremely wide interpretation of the words "similar limited area" can not be applied in relation to Cl. 16-1, sub-clause 2. To the contrary Cl. 16-1, sub-clause 2 (b), must be read more in line with the York-Antwerp Rules' concept as a place where the vessel can be safely moored similar to when in port.
It is probably of no importance to carry this analysis any further as the "physical obstruction" requirement will be the most important one in practice. If the whole Arabian Gulf should be considered as a "similar limited area" per Cl. 16-1, sub-clause 2 (b), it is hardly conceivable that the entrance to the Gulf, the Hormuz-Strait, could be blocked by a physical obstruction caused by a marine peril. If there is a physical obstruction caused by a marine peril preventing the vessel from leaving an area, that should suffice for the purpose of applying Cl. 16-1, sub-clause 2 (b), and there is no need to restrict the cover further by introducing a narrow interpretation of the words "similar limited area".