TJOFLAT, Circuit Judge:

I.

A.

This negligence suit under Georgia law stems from an injury Roland Walker suffered as he unloaded freight from a railcar in July 2005. At that time, Walker worked for Exel, Inc., the operator of a shipping and receiving facility in Fairburn, Georgia,1 which exclusively receives deliveries of food products from Unilever Bestfoods of North America ("Unilever") on behalf of local Fairburn businesses. On July 22, the railcar arrived at Exel loaded with fifty-six pallets of containers of Unilever-produced mayonnaise that Unilever had loaded and shipped from its Chicago facility. The railcar was delivered by rail carrier CSX Transportation, Inc. ("CSX");2 the car was, however, the property of another rail carrier, Norfolk Southern Railway Company and Norfolk Southern Corporation (collectively, "Norfolk Southern").3

The railcar was equipped with two interior bulkhead doors, or "interior load divider partitions," that allowed the car to be divided into three sections — a center compartment and two side compartments — for the organized loading of freight.4 The bulkhead doors, each weighing 1,000 pounds, were suspended from the railcar's interior ceiling by a carriage assembly that rolled along a parallel set of ceiling and floor tracks that ran the length of the railcar. To load and unload one of the side compartments behind a bulkhead door, an individual would move the door back and forth within the railcar along the door's track system by squeezing a handle, or "release latch," in the center of the door, which would cause four spring-loaded "locking pins," one in each of the door's corners, to retract from receptacles in the lower and upper tracks along which the door operated. Once the locking pins were disengaged, the door could be pushed or pulled freely along its tracks. Thus, when a side compartment of the railcar was loaded with cargo, a bulkhead door would be operated in this way and positioned tightly against the cargo to hold it securely in place during transit. The door would then be locked against the cargo by releasing the door's latch, causing the spring-loaded locking pins to extend back into the track receptacles5 — the tracks contained numerous receptacles, allowing the bulkhead door to be locked throughout most of the railcar. In turn, to unload the compartment behind a locked bulkhead door, an individual would squeeze the door's release latch to retract the locking pins, allowing the door to be pushed or pulled down the tracks and away from the stored cargo.

Exel assigned employee Rodney Thomas to unload the pallets of mayonnaise containers from the railcar. Thomas commenced the unloading process by opening the railcar's exterior door, at which time he discovered that the pallets Unilever had loaded in the car's center compartment — sixteen in total — had shifted during transit. As a result, Thomas, prior to unloading the pallets, took photographs to evidence the load shift, anticipating that a claim for loss of product might later arise. He then unloaded the pallets using a forklift.

After that, Thomas sought to unload the pallets loaded in the side compartments behind the two interior bulkhead doors; twenty pallets were loaded behind each door. When Thomas squeezed the doors' release latches, however, he discovered that the doors' locking systems were "jammed," that is, that their locking pins would not easily retract from the receptacles in the ceiling tracks. Thomas then saw Walker working nearby, so he asked Walker if he would assist him in opening the doors; Walker agreed to help and entered the railcar.6 The two men then proceeded to try to disengage one of the doors: Thomas moved the release latch back and forth in an attempt to loosen it, while Walker grabbed onto the door's frame and pulled.

Soon the bulkhead door's locking pins retracted. Once that happened, however, the door rushed forward at Walker and Thomas. As it was later discovered, as with the center compartment, several of the pallets of mayonnaise containers loaded behind the door had shifted during transport, causing ten to twelve of the pallets — weighing between 18,000 and 22,000 pounds7 — to fall against the door and to propel the door forward along its tracks. Thomas immediately released the door's latch, yet the locking pins did not extend back into the track receptacles, and the door continued to charge rapidly at the two men. Thomas, who was positioned near the railcar's exterior door, quickly jumped from the car, but Walker was not able to do so and was struck by the bulkhead door. The door's force then drove Walker into the other interior door, pinning him between the two.8

Paramedics eventually released Walker from the doors' clasp, but only after Thomas and other Exel coworkers had removed the fallen pallets of mayonnaise containers from behind the door in order to push the door back along its tracks. As a result of his crushing accident, Walker suffered severe injuries to his shoulder, chest, and leg, all of which required extensive medical care and treatment.9

B.

On June 11, 2007, Walker sued CSX for negligence;10 he subsequently amended his complaint on June 29, 2007, to add Norfolk Southern as a defendant.11 In his amended complaint, Walker claimed that Norfolk Southern and CSX (collectively, "Defendants") were jointly and severally liable for his injury in negligence, and he sought compensatory damages. Walker alleged that Defendants had not regularly inspected and maintained the interior bulkhead door's locking system prior to his injury, despite having had multiple opportunities to do so when the car had been in their possession. These omissions were negligent, Walker asserted, because regular inspections and maintenance of the door were required under Georgia common law and various rules and guidelines issued by the Association of American Railroads (the "AAR"), a private railroad-industry trade association to which Defendants belong. Moreover, this negligence, Walker claimed, had caused his injury, since reasonably discoverable and curable defects in the door's locking system — which Walker's complaint characterized as a "safety mechanism" — had kept the locking system from functioning properly at the time of his injury. According to Walker, had the locking system worked as intended and not been defective, it would have averted his injury by bringing the door to a dead stop once Thomas released the door's latch.

1.

To corroborate his allegations as to the cause of his injury, Walker, during discovery, retained a putative railcar expert named Michael Micek.12 Micek opined, both in a written report and on deposition, that the bulkhead door's locking system was, in fact, designed as a "fail-safe safety device" to protect workers like Walker, since the locking pins were spring-loaded. Thus, Micek stated, if, as here, cargo fell against the door, causing it to charge forward along its tracks,13 the locking pins were designed to extend back into the track receptacles once the door's latch was released and to instantly retard the door's movement. Hence, in Micek's opinion, had the locking system functioned properly, as soon as Thomas released the door's latch, the locking pins would have inserted themselves into the track receptacles and stopped the door's rush, notwithstanding that 18,000 pounds or more of fallen cargo were pressing the door forward. The locking system, however, did not function in that intended way, Micek posited, because the door's locking system had become defective due to poor maintenance by Defendants. That is, according to Micek, "[t]he root cause of th[e] accident ... was the mechanical imperfections and defective conditions of the locking rails," and the fact that thousands of pounds of shifted cargo were pressing against the door and propelling it down the track "doesn't matter."14

2.

After discovery closed, Norfolk Southern moved the district court to exclude from evidence Micek's proposed expert testimony, challenging Micek's qualifications as an expert under Federal Rule of Evidence 70215 and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993). Additionally, Defendants moved for summary judgment under Federal Rule of Civil Procedure 56,16 arguing that they were entitled to judgment as a matter of law because the record evidence raised no triable issues of fact for the jury as to whether Defendants were liable under Georgia negligence law.17 The district court ruled on all the motions in the same order.

First, the court granted Norfolk Southern's motion to exclude Micek's expert testimony.18 Norfolk Southern had argued that Micek's expert opinions should be excluded because they were not scientifically based, premised upon sound methodology, or concerned with areas with which Micek had significant experience based on his prior occupations. In particular, Norfolk Southern had challenged Micek's basis for testifying that the bulkhead door's locking system was designed as a safety device that could reengage and stop the movement of the door as 18,000 pounds or more of cargo fell against it. In ruling on the motion, the court correctly sided with Norfolk Southern, holding that, in short, Walker "ha[d] not met [his] `burden of establishing qualification, reliability, and helpfulness'" of Micek's expert opinions. Order 8, July 29, 2010 (quoting United States v. Frazier, 387 F.3d 1244, 1260 (11th Cir.2004)).19

The court then granted Defendants' motions for summary judgment, holding that the record evidence was insufficient to raise a triable issue of fact on various elements necessary for Walker to prevail on his negligence claims. In Georgia, a negligence plaintiff must establish four elements:

Booth v. Quality Carriers, Inc., 276 Ga.App. 406, 623 S.E.2d 244, 246 (2005) (quoting Heston v. Lilly, 248 Ga.App. 856, 546 S.E.2d 816, 818 (2001)). However, the evidence here, the district court ruled, was insufficient for a jury to reasonably infer either that Defendants had breached a legal duty of care by failing to regularly inspect and maintain the bulkhead door or that those omissions, even if negligent, proximately caused Walker's injury. Accordingly, the court dismissed Walker's claims against Defendants as a matter of law. Walker now appeals.

II.

In his brief on appeal, Walker challenges only that portion of the district court's order granting Defendants summary judgment.20 He claims that the district court erred because there is a triable issue as to whether Defendants were negligent in failing to regularly inspect and maintain the bulkhead door. Walker's argument is based on various AAR rules and guidelines that, he says, required Defendants, as AAR members, to inspect and maintain the bulkhead door annually.21 Walker declares that, under Georgia law, the district court erred in not considering these privately established rules as "illustrative of [the defendants'] negligence" and thus as creating a question of fact for the jury. See, e.g., Luckie v. Piggly-Wiggly S., Inc., 173 Ga.App. 177, 325 S.E.2d 844, 845 (1984) ("Privately established rules are admissible as illustrative of negligence, but the violation of such a rule is not negligence in and of itself." (internal quotation marks omitted)). We need not assess whether Walker's argument has merit, however, because it plainly ignores the conspicuous fact that, as the district court held, the record lacks evidence that Defendants' omissions, even if negligent, were a proximate cause of his injury. That is, as explained in the following discussion, even if we assume arguendo that Defendants were negligent, we must affirm the district court's summary judgment.

Negligence is not actionable under Georgia law unless that negligence was a proximate cause of the plaintiff's injury. See Anderson v. Barrow Cnty., 256 Ga.App. 160, 568 S.E.2d 68, 71 (2002) ("[N]o matter how negligent a party may be, if his act stands in no causal relation to the injury it is not actionable." (quoting Bacon v. Mayor & Aldermen of City of Savannah, 241 Ga.App. 211, 525 S.E.2d 115, 117 (1999) (internal quotation marks omitted))); Davis v. Aiken, 111 Ga.App. 505, 142 S.E.2d 112, 115-16 (1965) ("Negligence alone does not give a right of action to an injured person against the negligent person unless the negligence be the proximate cause of the injury and damage."). Proximate causation reflects a policy-based evaluation of whether the negligent defendant should be held legally responsible for the plaintiff's injury, or whether, instead, "the defendant's conduct and the plaintiff's injury are too remote for the law to countenance recovery." Atlanta Obstetrics & Gynecology Grp., P.A. v. Coleman, 260 Ga. 569, 398 S.E.2d 16, 17 (1990) (internal quotation mark omitted). It is "another way of saying ... that the defendant was under no duty to protect the plaintiff from the injury which in fact occurred." McAuley v. Wills, 251 Ga. 3, 303 S.E.2d 258, 261 (1983) (citing William L. Prosser, The Law of Torts 244 (4th ed.1971)).

No universal formula governs proximate-cause analysis. Coleman, 398 S.E.2d at 17. Rather, it is a mixed question of law and fact "to be determined on the facts of each case upon mixed considerations of logic, common sense, justice, policy and precedent." Id. Typically, therefore, the inquiry is appropriately left to the jury. See id. ("[Determining] whether proximate cause exists ... requires both fact-finding in the `what happened' sense, and an evaluation of whether the facts measure up to the legal standard set by precedent. Ordinarily, both determinations are most appropriately made by a jury upon appropriate instructions from the judge."). Yet, the question should be answered by the court as a matter of law "in plain and undisputed cases," id. at 17-18, that is, in cases where "the evidence shows clearly and palpably that the jury could reasonably draw but one conclusion, that the defendant's acts were not the proximate cause of the injury." Atlanta Gas Light Co. v. Gresham, 260 Ga. 391, 394 S.E.2d 345, 347 (1990) (internal quotation mark omitted). This is such a case.

Since Walker's negligence claim proceeds on his theory that Defendants breached duties to inspect and maintain the bulkhead door's locking system, in order to satisfy the proximate-cause element and survive summary judgment, there must be evidence reasonably linking his injury to a discoverable and curable defect in the door's locking system. Cf. Ken Thomas of Ga., Inc. v. Halim, 266 Ga.App. 570, 597 S.E.2d 615, 618 (2004) (holding, in part, that trial court erred in not granting summary judgment to defendant car dealership in negligence lawsuit because evidence did not support inference that plaintiff's accident, resulting from steering malfunction in car loaned by defendant, was proximately caused by defendant's negligent failure to repair or maintain car); Jordan v. Atlanta Replex Corp., 228 Ga.App. 670, 492 S.E.2d 536, 540 (1997) (explaining that summary judgment is proper in slip-and-fall cases alleging defendant's negligent maintenance of premises if plaintiff does not present evidence creating a material issues of fact as to whether a defect caused fall and whether such defect was the consequence of defendant's breach of its duty to maintain premises); Davis, 142 S.E.2d at 117-18 (explaining that a plaintiff, to plead that defendant's negligent failure to make an adequate inspection was a proximate cause of plaintiff's injury, must allege that a defective condition existed that caused the injury and "that an inspection would have discovered the defect"). That is, the evidence must indicate that: (1) at the time of Walker's injury, the door's locking system was defective; (2) the defective condition existed due to Defendants' negligence; and (3) the defect resulted in Walker's injury.

The record evidence, however, does not reasonably connect Walker's injury to a defect in the door's locking system birthed by any negligence on the part of Defendants. None of the evidence in the record supports the accuracy of Walker's characterization of the locking system as a safety device that was intended to reengage and halt the door's movement when cargo — in this case, 18,000 pounds or more of cargo — pushed the door rapidly forward along its tracks; nor does the evidence suggest that the locking system was otherwise capable of functioning in that way.22 Indeed, as recognized by the district court as well, the only evidence that supported Walker's impression of the locking system's intended design was the putative expert opinion of Micek, testimony that is properly no longer part of the record because it is too speculative and unreliable. See Order 7, July 29, 2010 ("Micek testified that because the locking pins are spring-loaded, they are designed as a `fail-safe safety device,' but there is nothing in the record that supports his opinion." (emphasis added)). As a result, the sole reasonable inference to be drawn from the evidence is that, under these facts, the locking system operated just as it had been designed to.23 Thus, the locking system's inability to stop the door's rapid charge cannot be attributed to a defect begot by Defendants' negligent omissions, since no frequency of inspection or maintenance would have enabled the locking system to do that which it could not do.24 Liability for Walker's injury, therefore, cannot be fairly traced to any negligence on Defendants' part in failing to annually inspect and maintain the door as required under the AAR rules and guidelines. Cf. Henson v. Georgia-Pacific Corp., 289 Ga.App. 777, 658 S.E.2d 391, 394-95 (2008) (upholding summary judgment for defendant in premises-liability case in which plaintiff alleged that the defendant negligently failed to maintain a freight elevator, the doors of which injured plaintiff, because plaintiff did not present any competent evidence that elevator doors were actually defective at the time of his injury); Davis, 142 S.E.2d at 117-18 ("If the inspection would not have discovered the defect, then the failure to inspect cannot be the proximate cause of any injury to the plaintiff."); see also, e.g., Mello v. K-Mart Corp., 792 F.2d 1228, 1233 (1st Cir.1986) (stating that, under Tennessee products-liability law, even if defendant was negligent in failing to test a product it offered for sale, "that negligence could not have been the proximate cause of the plaintiffs' injuries, because no amount of testing would have weeded out what ... was a non-defective" product (emphasis in original)). To rule otherwise would require us to unreasonably draw unsupported inferences as to how Defendants' omissions could have caused Walker's accident.25 See Marshall v. City of Cape Coral, 797 F.2d 1555, 1559 (11th Cir.1986) (stating that, although "[a]ll reasonable inferences arising from the evidence must be resolved in favor of the non-movant, ... inferences based upon speculation are not reasonable") (citing Blackston v. Shook & Fletcher Insulation Co., 764 F.2d 1480, 1482 (11th Cir.1985)).

Based on the foregoing, the district court was correct in granting Defendants summary judgment. Walker presented no evidence from which a jury could infer that Defendants' omissions, even if negligent, were a proximate cause of his injury, an essential element of his negligence claim under Georgia law. See United States v. Four Parcels of Real Prop., 941 F.2d 1428, 1438 (11th Cir.1991) ("If the nonmoving party fails to `make a sufficient showing on an essential element of her case with respect to which she has the burden of proof,' the moving party is entitled to summary judgment.") (quoting Celotex Corp. v. Catrett, 477 U.S. 317, 323, 106 S.Ct. 2548, 2552, 91 L.Ed.2d 265 (1986)). The district court's judgment is therefore

AFFIRMED.