Does a public entity have a duty to take reasonable steps to protect the public from the danger?

Where a public entity has actual or constructive notice of a dangerous condition, it has a duty to take reasonable steps to protect the public from the danger even if such dangers are not necessarily created by the entity. (Swaner v. City of Santa Monica, supra, 150 Cal.App.3d at p. 807, 198 Cal.Rptr. 208.) "[P]laintiffs must allege foreseeability before they can successfully recover from a public entity for injuries caused by the lack of a barrier." (Id., at p. 810, 198 Cal.Rptr. 208.) When facts disclose such foreseeable circumstances, "the question of the reasonableness of a public entity's action in any [such] particular situation is one of fact for a jury." (Id., at pp. 810, 813, 198 Cal.Rptr. 208.)