In Hooker v. Department of Transportation (2002) 27 Cal.4th 198, the California Department of Transportation (CALTRANS) hired a contractor to construct an overpass. The contractor's employee was killed while operating a crane. It was alleged CALTRANS was liable for the death of the crane operator because it allowed traffic to use the overpass during construction, which lead to the crane operator's death. The question presented was whether an employee of a contractor may sue the hirer of a contractor for the tort of negligent exercise of retained control. (Id. at p. 201.) "We conclude that a hirer of an independent contractor is not liable to an employee of the contractor merely because the hirer retained control over safety conditions at a worksite, but that a hirer is liable to an employee of a contractor insofar as a hirer's exercise of retained control affirmatively contributed to the employee's injuries. In this case, although plaintiff raised triable issues of material fact as to whether defendant retained control over safety conditions at the worksite, plaintiff failed to raise triable issues of material fact as to whether defendant actually exercised the retained control so as to affirmatively contribute to the death of plaintiff's husband. Therefore, the trial court properly granted summary judgment in favor of defendant, and the Court of Appeal erred in reversing that judgment." (Hooker, supra, 27 Cal.4th at p. 202.) The California Supreme Court considered whether the hirer of an independent contractor can be held liable for on-the-job injury to the contractor's employee where the hirer negligently exercised retained control over safety conditions at the worksite. The Hooker court concluded the hirer is not liable to the contractor's employee merely because the hirer retained control over safety conditions on the worksite, but is liable to the employee if its "exercise of retained control affirmatively contributed to the employee's injuries." (Hooker, supra, 27 Cal.4th at p. 202.) The court reasoned that "because the liability of the contractor, the person primarily responsible for the worker's on-the-job injuries, is limited to providing workers' compensation coverage, it would be unfair to impose tort liability on the hirer of the contractor merely because the hirer retained the ability to exercise control over safety at the worksite. In fairness, . . . the imposition of tort liability on a hirer should depend on whether the hirer exercised the control that was retained in a manner that affirmatively contributed to the injury of the contractor's employee." (Id. at p. 210.) In that case, the Supreme Court held that a hirer of an independent contractor is not liable to an employee of the contractor merely because the hirer retained control over safety conditions at a worksite; such liability could arise only if the hirer's exercise of retained control affirmatively contributed to the employee's injuries. In that case, Hooker had worked as a crane operator employed by a general contractor hired by the California Department of Transportation (CalTrans) to construct an overpass. The overpass was 25 feet wide and the crane with the outriggers extended was 18 feet wide, so Hooker had to retract the outriggers to allow other vehicles, including CalTrans vehicles, to pass by the construction site. Shortly before the fatal accident, Hooker retracted the outriggers and left the crane. When he returned, he attempted to swing the boom, without first reextending the outriggers. Because the outriggers were retracted, the weight of the boom caused the crane to tip over, killing Hooker. ( Hooker, supra, 27 Cal.4th at p. 202.) The plaintiff, Hooker's widow, sued CalTrans, claiming it had negligently exercised the control it had retained over safety at the jobsite. The plaintiff relied upon the safety chapter of the CalTrans construction manual, as well as the testimony of CalTrans officials. The safety chapter stated that " 'CalTrans is responsible for obtaining the Contractor's compliance with all safety laws and regulations. . . .The construction safety coordinator must be familiar with highway construction procedures and equipment, construction zone traffic management and be able to recognize and anticipate unsafe conditions created by a Contractor's operation. . . .The Construction Safety Coordinator shall visit contracts periodically to observe the Contractor's operation and traffic conditions affected by the construction.' The manual further gave the CalTrans resident engineer authority to set compliance schedules for the correction of dangerous conditions and to shut down affected operations until the dangerous conditions were corrected." ( Hooker, supra, 27 Cal.4th at p. 202.) Prior to the accident, the CalTrans representative with responsibility for safety at this jobsite had observed the crane operators on the project retract their outriggers to let other vehicles pass; he knew the crane would be unstable if its boom were extended to the side when its outriggers were retracted. ( Id. at pp. 202-203.) Hooker explained that in Camargo v. Tjaarda Dairy (2001) it (the Supreme Court) had barred an employee of a contractor from suing the hirer of the contractor for negligent hiring because the liability of the hirer would derive " ' "from the 'act or omission' of the hired contractor . . . who caused the injury by failing to use reasonable care in performing the work." . . . "It would be unfair to impose liability on the hiring person when the liability of the contractor, the one primarily responsible for the worker's on-the-job injuries, is limited to providing workers' compensation coverage." ' " ( Hooker, supra, 27 Cal.4th at pp. 205-206, 210.) Hooker then applied this reasoning to the issue of retained control. "Similarly, because the liability of the contractor, the person primarily responsible for the worker's on-the-job injuries, is limited to providing workers' compensation coverage, it would be unfair to impose tort liability on the hirer of the contractor merely because the hirer retained the ability to exercise control over safety at the worksite. In fairness, . . . the imposition of tort liability on a hirer should depend on whether the hirer exercised the control that was retained in a manner that affirmatively contributed to the injury of the contractor's employee." (Hooker, at p. 210.) The court noted that there also would be times when such an affirmative contribution could be in the form of an omission, such as if a hirer promised to undertake a particular safety measure but then failed to do so, resulting in injury to a contractor's employee. (Id. at p. 212, fn. 3.) The Supreme Court determined that CalTrans could not be held liable for Hooker's injuries simply because CalTrans had permitted traffic to use the overpass while the construction was ongoing. The court found that although the plaintiff had raised triable issues of fact as to whether CalTrans retained control over safety conditions at the worksite, plaintiff had failed to raise triable issues whether CalTrans actually exercised the retained control so as to affirmatively contribute to the death of plaintiff's husband. ( Hooker, supra, 27 Cal.4th at pp. 214-215.) The court's holding was based in part on section 414 of the Restatement Second of Torts, which states: "One who entrusts work to an independent contractor, but who retains the control of any part of the work, is subject to liability for physical harm to others for whose safety the employer owes a duty to exercise reasonable care, which is caused by his failure to exercise his control with reasonable care." (Rest.2d Torts, 414, quoted in Hooker, supra, 27 Cal.4th at pp. 201, 206.) In short, the defendant agency had retained control of the work. The Supreme Court held that a hirer of an independent contractor can remain liable to the contractor's injured employee if the hirer not only retains control over the details of the work but exercised that control in a manner that "affirmatively contributed" to the employee's injuries. (Hooker, supra, 27 Cal.4th at p. 210.) An affirmative contribution can occur, for example, by actively directing the contractor or its employees, or by promising to undertake a particular safety measure and then negligently failing to do so, resulting in an employee's injury. (Id. at p. 212, fn. 3.) Merely retaining the ability to control or direct the work, without the actual exercise of that authority, is insufficient to impose liability on the hirer. (Id. at p. 215) The Court held that 1 "a hirer of an independent contractor is not liable to an employee of the contractor merely because the hirer retained control over safety conditions at a worksite, but that a hirer is liable to an employee of a contractor insofar as a hirer's exercise of retained control affirmatively contributed to the employee's injuries." (Id. at p. 202.) The court's holding was based in part on section 414 of the Restatement Second of Torts, which states: "One who entrusts work to an independent contractor, but who retains the control of any part of the work, is subject to liability for physical harm to others for whose safety the employer owes a duty to exercise reasonable care, which is caused by his failure to exercise his control with reasonable care." (Rest.2d Torts, 414, quoted in Hooker, supra, 27 Cal. 4th at pp. 201, 206.)