The Department of Transportation, Bureau of Driver Licensing (the department) appeals an order of the Court of Common Pleas of Cambria County dated April 6, 1990, which sustained the appeal of Arthur J. Gaertner (Gaertner) from a department order suspending Gaertner’s operating privilege for one year pursuant to 75 Pa.C.S. § 1547 for failure to submit to a blood test.
*425On August 28, 1989, Johnstown police officer Andrew Litvin saw Gaertner run a red light. Gaertner then crossed the center line of the road and hit a parked car. As Officer Litvin approached the car to see if Gaertner was injured, he became aware that Gaertner was hearing-impaired because he had to tap Gaertner on the shoulder to get his attention and because Gaertner did not seem to understand what he was saying unless they were directly facing one another. While speaking to Gaertner, Officer Litvin detected a strong odor of alcohol about Gaertner’s person, noticed Gaertner’s eyes were glassy and blood shot, and that he was unsteady on his feet. Officer Litvin asked Gaertner to submit to a blood test to determine the alcohol content in his blood and Gaertner refused. Having probable cause to believe that Gaertner was driving under the influence of alcohol, Officer Litvin arrested Gaertner and transported him to the police station.
Upon arrival at the station, Officer Litvin began the booking process. Officer Litvin was able to communicate with Gaertner to obtain basic information such as age, height, weight, address and the like. Litvin would point to the space provided for such information and Gaertner would answer. Officer Litvin again asked Gaertner if he would submit to a chemical test and Gaertner replied that he would not. Litvin telephoned the Hiram G. Andrews Center where Gaertner is a client and asked if an interpreter was available that he could use. Officer Litvin was informed that there were no interpreters on call. Litvin then asked for someone from the center to come and pick up Gaertner because he had been arrested. When Mr. Richard Statnick, an employee of the center, arrived, Officer Litvin again asked Gaertner to submit to chemical testing. Officer Litvin wrote a statement asking whether Gaertner would submit to a blood test to determine if he was intoxicated. The statement further provided that if Gaertner refused, he would lose his license for one year. Underneath this statement were two separate lines, one which read “I will submit to the test” and another which read “I will not submit to the *426test.” Mr. Gaertner placed an X next to the line refusing the test and signed the statement. The department, by order dated September 27, 1989, notified Gaertner that his operating privilege was to be suspended for one year pursuant to 75 Pa.C.S. § 1547 for failing to submit to chemical testing.
Gaertner appealed the department’s order to the Court of Common Pleas of Cambria County and a de novo hearing was held on March 12, 1990. Officer Litvin testified to the events leading up to the arrest and the communications he had with Gaertner while at the site of the accident and at the police station. Mr. Statnick testified to the statement written by Officer Litvin and his observations of Gaertner. Gaertner himself testified through an interpreter that his refusal was not knowing and conscious because he needed an interpreter, regardless of the fact that he never requested one. He further stated that he did not understand the words submit, determine, or intoxicated as used in officer Litvin’s written statement. Ms. Shirley Bassett also testified. She was qualified as an expert in the field of deaf and hearing impaired communications and testified that deaf people normally have a sixth to eighth grade educational level. She further stated that after talking to Gaertner she was of the opinion that he does not have a good command of the English language and could understand only simple words and simple sentences composed of three or four words. Finally, Ms. Bassett stated that she did not believe Gaertner could have understood the statement written by Officer Litvin without the services of an interpreter. The Honorable Thomas Swope, after hearing all of the testimony, concluded that Gaertner, in fact, needed an interpreter to make a knowing and conscious refusal. Thus, the court sustained Gaertner’s appeal and rescinded the department’s order suspending Gaertner’s operating privilege. A timely appeal by the department was brought to this Court.
As an appellate court, we must confine our review to whether the findings of fact are supported by competent evidence, whether there has been an error of law, or wheth*427er the trial court abused its discretion. Gresh v. Department of Transportation, Bureau of Traffic Safety, 76 Pa.Commonwealth Ct. 483, 464 A.2d 619 (1983).
Neither party disputes the fact that the department has met its initial burden of proving that the motorist (1) was arrested for driving while intoxicated, (2) was requested to submit to chemical testing, (3) refused to so submit, and (4) was informed that such refusal would result in suspension of his license. Schnitzer v. Commonwealth, 85 Pa.Commonwealth Ct. 38, 480 A.2d 388 (1984). Once the department has sustained its burden of proof to establish a refusal under 75 Pa.C.S. § 1547, the burden then shifts to the motorist to show that his refusal was not the product of a knowing and conscious decision. Department of Transportation, Bureau of Traffic Safety v. O’Connell, 521 Pa. 242, 555 A.2d 873 (1989). The question of whether a motorist’s decision to refuse chemical testing was knowing and conscious is a question of fact for the trial court. Capozzoli Appeal, 63 Pa. Commonwealth Ct. 411, 437 A.2d 1340 (1981). Because of our limited scope of review, we are bound by the trial court’s findings of fact unless they are not supported by substantial evidence or constitute an error of law.
The primary issue for our consideration is whether the trial court abused its discretion or erred as a matter of law in finding that a deaf motorist met his burden of proving that his refusal to take a blood test was not the product of a knowing and conscious decision.
The department relies upon Department of Transportation, Bureau of Driver Licensing v. Peck, 132 Pa.Commonwealth Ct. 509, 573 A.2d 645 (1990), for support of its proposition that Gaertner has, as a matter of law, failed to sustain his burden of proof. In Peck, the motorist, after an arrest for drunk driving, argued that his refusal to submit to chemical testing was not knowing and conscious because he suffers from a learning disability which renders him incapable of functioning under stress; he has what amounts to diminished capacity and was, therefore, unable to under*428stand the consequences of refusing the test. We rejected the motorist’s argument in Peck based on our conclusion that such a finding was not supported by substantial evidence. The expert psychologist who testified for Peck did not expressly rule out alcohol as a contributing factor to the confusion nor did he express the opinion that Peck’s learning disability actually prevented him from making a knowing and conscious refusal.
Gaertner finds support for his argument that his refusal was not knowing and conscious in Department of Transportation, Bureau of Motor Vehicles v. Yi, 128 Pa.Commonwealth Ct. 117, 562 A.2d 1008 (1989). There, we upheld a rescission of a driver’s license suspension because the motorist’s refusal was not knowing and conscious. The motorist, Yi, was a non-English speaking immigrant. He testified át trial through an interpreter that he had no understanding of the English language and, therefore, did not and could not understand the ramifications of his refusal to submit to chemical testing upon his arrest for drunk driving. The trial judge credited Yi’s testimony that he, in fact, was unable to understand English and, therefore, could not have made a knowing and conscious refusal. This particular factual finding by the trial judge was held to constitute substantial evidence.
While Gaertner maintains that Yi is controlling because sign language is akin to a foreign language, the department contends that the present case is clearly distinguishable from Yi and more in line with Peck. The department argues that Gaertner has a considerably greater command of the English language than the immigrant had in Yi. In Yi, the motorist did not understand any English and here, Gaertner has at least a sixth to eighth grade command of the written English language. The department maintains that a sixth or eighth grade educational level amounts to diminished intellectual capacity and under Peck, intellectual immaturity does not provide a license to disregard the driving rules. On the other hand, Gaertner argues that he has a language deficiency, not a mental defect or incapacity, *429and this deficiency could have easily been remedied by using an interpreter.
We think that the case before us straddles the fine line between Yi and Peck, two cases where the inability to understand is asserted as a defense but where it prevails in one and fails in the other. This case, we think, falls closer to Yi in a number of respects. First, the immigrant in Yi was unable to testify at trial without an interpreter. Similarly here, Gaertner needed an interpreter at trial to understand the proceedings as well as to respond to all questions. Secondly, the language deficiency of Gaertner does not necessarily amount to intellectual immaturity nor is it properly labelled a learning disability. The motorist in Peck claimed that his learning disability manifested itself in the form of improper intellectual functioning under stress. A logical deduction from this statement is that in non-stressful situations his intellectual functioning is unhampered. In the case before us, however, Gaertner’s hearing impairment is a constant hindrance when dealing with hearing persons regardless of the level of stress in the situation; his inability to understand the spoken or written word above a simplistic level is not something which can be triggered by the occurrence or non-occurrence of a particular event.
Perhaps the most compelling reason in this case which leads us to affirm the trial court bears on our standard of review. Whether one has made a knowing and intelligent refusal to submit to chemical testing is a question of fact for the trial court. Capozzoli Appeal. As fact finder, the trial judge is required to evaluate the witnesses, their demeanor and make the necessary credibility determinations. Im v. Department of Transportation, 108 Pa.Commonwealth Ct. 206, 529 A.2d 94 (1987). These credibility determinations cannot be disturbed on appeal if they are supported by substantial evidence. Im. In the case at bar, the trial judge, after hearing testimony by the witnesses, specifically credited Gaertner’s testimony when he stated in his opinion “Petitioner was not aware of what was going on, nor the consequences of his actions when he signed the *430paper given him by Officer Litvin.” (Opinion of the Trial Court, slip op. at 5.) Furthermore, the trial court credited the testimony of Shirley Bassett, the expert in deaf communications, when the court found “very persuasive the expert testimony of Shirley Bassett.” Id. In our review of the record, we find the necessary substantial evidence to support the factual findings made by the trial court. Given the foregoing, we affirm.
ORDER
NOW, March 11, 1991, the order of the Court of Common Pleas of Cambria County, dated April 6, 1990, at No. 1989-2536 is hereby affirmed.