What danger does this vertical traffic sign warn us of as we approach a particular section?

Question

DentroTest · Accepted Answer

Sign P-31 (Traffic congestion) warns of the proximity of a section where traffic is frequently stopped or hindered by congestion. On seeing it, it is advisable to reduce speed in advance, increase the safety distance from the vehicle ahead and warn those behind of braking with the brake lights. That traffic changes to a single direction is not warned of by this sign: one-way traffic is indicated by S-11 (One-way single-lane carriageway), which is an information sign. Nor does it warn of a roadway blocked by vehicles obstructing it, a different danger warned of by P-32 (Obstruction on the carriageway), but of dense or held-up traffic.

What danger does this vertical traffic sign warn us of as we approach a particular section?

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