opinion: PER CURIAM.
  On special interrogatories the jury found that the concurrent negligence of Lahey and Lovejoy was the proximate cause of the accident in which Humphrey and Joanne Collins, later Mrs. Lovejoy, sustained substantial injuries. The jury also determined that Humphrey did not assume a known risk of injury and that he was not guilty of contributory negligence and that Lahey was in the employ of Emery Transportation Company (Emery), the appellant here, and that he was acting in the scope of his employment at the time of the accident, while Humphrey was not. It is the contention of Emery that an independent act of negligence on the part of Lovejoy was a superseding cause of the accident, thereby insulating Emery from liability. Jurisdiction in the suit was based on diversity and an amount in controversy exceeding $3,000. All the operative facts took place in Pennsylvania and the law of Pennsylvania governs.
  The law of Pennsylvania in respect to superseding cause is clear and is stated in Jeloszewski v. Sloan, 1953, 375 Pa. 360, 100 A.2d 480, 482, quoting with approval from Kline v. Moyer, 1937, 325 Pa. 357, 364, 191 A. 43, 46, 111 A.L.R. 406, as follows: “ ‘Where a second actor has become aware of the existence of a potential danger created by the negligence of an original tort-feasor, and thereafter, by an independent act of negligence, brings about an accident, the first tort-feasor is relieved of liability, because the condition created by him was merely a circumstance of the accident and not its proximate cause. Where, however, the second actor does not become apprised of such danger until his own negligence, added to that of the existing perilous condition, has made the accident inevitable, the negligent acts of the two tort-feasors are contributing causes and proximate factors in the happening of the accident and impose liability upon both of the guilty parties.’ ”
  The principle stated is dispositive of the instant appeals and accordingly the judgments will be affirmed.
instruction: What follows is an opinion from a United States Court of Appeals.
  Intervenors who participated as parties at the courts of appeals should be counted as either appellants or respondents when it can be determined whose position they supported. For example, if there were two plaintiffs who lost in district court, appealed, and were joined by four intervenors who also asked the court of appeals to reverse the district court, the number of appellants should be coded as six.
  When coding the detailed nature of participants, use your personal knowledge about the participants, if you are completely confident of the accuracy of your knowledge, even if the specific information is not in the opinion. For example, if "IBM" is listed as the appellant it could be classified as "clearly national or international in scope" even if the opinion did not indicate the scope of the business. 
  
  Your task concerns the first listed appellant. The nature of this litigant falls into the category "private business (including criminal enterprises)", specifically "transportation". Your task is to determine what subcategory of business best describes this litigant.
choices: railroad boat, shipping shipping freight, UPS, flying tigers airline truck, armored cars other unclear