DISSENTING.
As I would hold that the statutory privilege set forth in 75 Pa.C.S. § 3754(b) does not prevent Appellee from compelling PennDOT to disclose to him the underlying facts and data within its accident investigations and safety studies for the purpose of preparing his criminal defense, I must respectfully dissent.
It is well established that evidentiary privileges, such as the privilege asserted by PennDOT in the instant case, are generally disfavored and should be narrowly construed. See Commonwealth v. Stewart, 547 Pa. 277, 690 A.2d 195, 197 (1997) (courts should accept privileges “only to the very limited extent that ... excluding relevant evidence has a public good transcending the normally predominant principle of utilizing all rational means for ascertaining the truth”) (internal quotation marks omitted). If the purpose for which a privilege was created is limited, the privilege applies only to the extent that it effectuates its purpose. See id. at 198-200.
As the majority notes, the primary question here involves the proper interpretation of 75 Pa.C.S. § 3754(b). In general, in interpreting statutes, we must attempt to ascertain and effectuate legislative intent. 1 Pa.C.S. § 1921(a); see O’Rourke v. Commonwealth, Dep’t of Corrections, 566 Pa. 161, 778 A.2d 1194, 1201 (2001). Where the words of the statute are clear and free from ambiguity, we must glean that legislative intent from the words of the statute. See 1 Pa.C.S. § 1921(b). However, we must also read the statute, if possible, to give effect to all of its provisions. Id. § 1921(a). Therefore, in accomplishing our goal of ascertaining legislative intent, we do not interpret the words of a statute in isolation *640from each other, but rather, in the context in which they appear. See O’Rourke, 778 A.2d at 1201. Thus, when parts of statutes relate to the same persons or things, or the same class of persons or things, they are in pari materia and are to be construed together. 1 Pa.C.S. § 1932; see Salazar v. Allstate Ins. Co.,, 549 Pa. 658, 702 A.2d 1038, 1041 (1997).
Section 3754 contains two subsections, both of which specifically refer to “in-depth accident investigations and safety studies.” See 75 Pa.C.S. § 3754(a), (b); slip op. at 4 n. 4 (quoting id. § 3754(a)), slip op. at 2-3 (quoting id. § 3754(b)). Subsection (a) empowers PennDOT to conduct accident investigations and safety studies “for the purpose of determining the causes of traffic accidents and the improvements which may help prevent similar ... accidents or increase the overall safety of roadways and bridges.” 75 Pa.C.S. § 3754(a). Subsection (b) limits the involvement of PennDOT in civil litigation over those investigations and studies and allows Penn-DOT to obtain candid information without fear of potential financial liability. See 75 Pa.C.S. § 3754(b).1 Accordingly, because both subsections relate to PennDOT’s authority to conduct accident investigations and safety studies, they are in pari materia and must be construed together. See 1 Pa.C.S. § 1932; Hamilton v. Unionville-Chadds Ford Sch. Dist., 552 Pa. 245, 714 A.2d 1012, 1015 (1998) (middle school discipline code and discipline section of school district’s student code were in pari materia because both applied to same subject matter, even though they did not apply to the same class of persons); Rosen v. Bureau of Prof'l & Occupational Affairs, State Architects Licensure Bd., 763 A.2d 962, 965-66 (Pa. Commw.Ct.2000) (Architects Licensure Law and the Engineer, Land Surveyor and Geologist Registration Law should be read in pari materia because the primary purpose of both statutes is the same).
*641In reading subsections (a) and (b) together, it is clear that the privilege set forth in subsection (b) relates to the purpose set forth in subsection (a), which is to improve traffic safety by empowering PennDOT to conduct investigations and safety studies. In other words, the protections created by subsection (b) exist to serve the purposes enunciated in subsection (a). Given this statutory construct, I agree with the Superior Court that the privilege set forth in subsection (b) is limited and may be given effect only to the extent necessary to further the purpose of allowing PennDOT to obtain accurate and honest information in its efforts to increase traffic safety without fear of incurring civil liability.2 See Stewart, 690 A.2d at 197 (evidentiary privileges should be applied only to the extent that they satisfy the public good). It is absolutely clear, at least in my view, that withholding facts and data from Appellee for use in the preparation of his defense against the criminal charges lodged against him does nothing to improve traffic safety. Thus, I disagree with the majority that the privilege at issue here is absolute and wholly protects Penn-DOT from disclosing all of the information Appellee seeks.
Like the trial court, however, I would restrict Appellee’s access to the information and limit its use “only for purposes connected with the preparation and presentation of the defense” of the criminal charges against Appellee. Trial Ct. Order, 3/9/98, at 2. I would also limit PennDOT’s disclosure to facts and data, and exclude all non-factual material from discovery. As now-President Judge Del Sole reasoned in his concurring and dissenting opinion below, facts and data gathered in accident investigations and safety studies do not, in and of themselves, subject PennDOT to the burdens of civil litigation. Rather, it is the opinions and conclusions formed by its employees and experts in reliance on those facts and data that expose PennDOT to potential civil liability, and therefore, it is those opinions and conclusions, rather than the *642facts and data themselves, that must be protected from disclosure.3
PennDOT argues, however, that any disclosure, including a limited disclosure such as the one I would permit in the instant case, would have a chilling effect on PennDOT’s ability to obtain candid and accurate information. This fear is simply unfounded. While I recognize the importance of allowing PennDOT to obtain such information without fear of liability, disclosing facts and data to Appellee for the sole purpose of defending his fundamental liberty interests would not in any way affect PennDOT’s ability to obtain information.4
Accordingly, I would vacate the order of the Superior Court and remand this matter to the trial court for an in camera review of PennDOT’s accident investigations and safety studies to determine the facts and data from these materials that must be disclosed to Appellee for the purpose of preparing and presenting his criminal defense.
Chief Justice CAPPY joins.. In light of the plain language of subsection (a), I, unlike the majority, do not believe that subsection (b) is clear and free from ambiguity as it relates to whether the privilege at issue here is absolute and applies to criminal prosecutions as well as civil proceedings.
. This interpretation of the statute’s purpose does not, as PennDOT alleges and the majority suggests, disregard the plain language of the statute. Rather, this interpretation stems directly from the very language of subsection (a). See 75 Pa.C.S. § 3754(a).
. Such disclosure would not "convert [PennDOT] into [A]ppellee's personal, but publicly-funded investigator, and additional expert,” as the majority states. Slip op. at 15. Rather, it would give Appellee's expert access to certain facts that Appellee would not be able to obtain otherwise, even with his own diligent investigation.
. I find PennDOT’s concern here a bit curious, given that it has already disclosed the construction and design records for the 1997 road improvements to Appellee. PennDOT fails to explain how allowing Appellee access to those records would not have the same chilling effect that it claims any disclosure of material within accident investigations and safety studies would cause.