2. ADAAG Background

The scope of the final regulatory analysis, applied to the Final Rules, can be viewed as consisting of several parts:

1. A restructuring of the 1991 ADAAG issued by the Access Board as final revised guidelines in 2004, containing 68 changed requirements identified and subjected to a regulatory analysis by the Access Board for purposes of estimating their annual capital costs in terms of new construction and alterations, approved by the Office of Management and Budget;
2. New requirements for certain State and local facilities first issued by the Access Board as final guidelines in 1998 and not subjected to final regulatory analysis by the Access Board; [1]
3. New requirements for play areas first issued by the Access Board as final guidelines in 2000 and subjected to a regulatory analysis by the Access Board to estimate the capital and operations and maintenance (O&M) costs of the new provisions for purposes of new construction and alterations (approved by the Office of Management and Budget);[2] and
4. New requirements for other recreational facilities first issued by the Access Board as final guidelines in 2002 and subjected to a regulatory analysis by the Access Board to estimate the capital costs of the new provisions for purposes of new construction and alterations (approved by the Office of Management and Budget).[3]

These different parts are now incorporated into the 2004 ADAAG, with the application and scoping provisions for all parts in ADA Chapters 1 and 2, and the technical requirements for all parts in the remaining chapters of the document.

The 2004 ADAAG imposes requirements for different types of construction: new construction, alterations and architectural barrier removal. New construction and alterations apply to new construction of buildings. Alterations involve major renovations at existing sites that are assumed to be undertaken on a regular basis to maintain building features to current levels of function, quality and style. Alterations differ from barrier removal in that barrier removal is assumed to be undertaken in response to a compliance measure and is smaller in scope.

2.1 Access Board Regulatory Assessment

In order to determine which of the requirements in the Final Rules represent a substantive change from the 1991 Standards, the Department relied primarily on the Access Board’s final regulatory assessment for the 2004 ADAAG, which was published in July 2004.[4]The Department also consulted the Board’s earlier regulatory assessments for its supplemental guidelines for play areas (2000) and recreation facilities (2002). [5] Because the costs of these supplemental guidelines had already been adopted into the ADAAG, they served as part of the Board’s baseline, and were not included in its 2004 regulatory assessment.

One difference between the Board’s regulatory assessments and the Department’s assessment is that the Board compared the provisions in the 2004 ADAAG to those in the 1991 ADAAG (as amended through 2002). The Department however must compare the provisions in the 2004 ADAAG (as ADA Standards) to currently enforceable law, represented primarily by the 1991 Standards (adopted in 1991 and amended in 1994). Although the 1991 Standards are consistent with the 1991 ADAAG, the two documents are not identical – there are some slight differences, both in the text of the requirements and as they have been interpreted and enforced by the Department. Because the purpose of the Department’s assessment is to determine how its adoption of the Final Rules will change the status quo, where a provision in the 2004 ADAAG was identified by the Board as a substantive change but is nonetheless consistent with the Department’s interpretation of the 1991 Standards and its enforcement practice, the Department’s adoption of that provision in the Final Rules represents not a substantive change but merely a codification of current law. [6]

In its regulatory assessment for the 2004 ADAAG, the Board has identified 68 requirements that represented a substantive change relative to the 1991 ADAAG (as amended through 2002) for purposes of newly constructed or altered facilities. [7] These changes were divided into three categories – “reduced cost” requirements, “no or minimal cost” requirements, and “increased cost” requirements. “Reduced cost” requirements include those for which the scoping or technical specifications for newly constructed or altered facilities have been made less stringent, or where new exceptions have been provided. “No or minimal cost” requirements include those that the Board determined would neither add new features or space nor present new design challenges when applied to newly constructed or altered facilities. Finally, the “increased cost” requirements include those that the Board determined would increase the cost of compliance for newly constructed or altered facilities, either by increasing the scoping requirement, making the technical specifications more stringent, or eliminating exceptions.

The Board then assessed the unit cost (the direct, one-time capital cost of making a given element or space compliant with a particular requirement) of each of the 14 requirements it had determined would impose an “increased cost” relative to the 1991 ADAAG (as amended through 2002), and, of those, selected 10 requirements that it determined were likely to have the greatest cost impact on newly constructed and altered facilities in four facility groups (office buildings, hotels, hospitals and long-term care facilities, and public housing). The Board selected these facility types based on its determination that half (or 7) of the 14 “increased cost” requirements would primarily affect these facilities, so that it could be assumed that these facilities were likely to experience relatively higher costs than other types of facilities. The Board aggregated the unit costs for these requirements on an annual basis as applied to all newly constructed and altered facilities in these four facility groups, and then extrapolated the results to all newly constructed and altered facilities generally.

In the ANPRM, the Department stated that it expected to “adopt” the Access Board’s final regulatory assessment for the 2004 ADAAG as its assessment of the cost impact that the Final Rules will have on newly constructed and altered facilities. At the same time, however, the Department recognized that its assessment of the costs for newly constructed and altered facilities would have to be broader than that of the Board. First, the Department’s assessment would have to include the costs associated with the supplemental guidelines, which, because they had been adopted by the Board in earlier rulemaking initiatives, had been considered part of the Board’s baseline. In addition, as the Department noted in the Regulatory Framework to the ANPRM, the unit costs estimated by the Board, though they could serve as a starting point, would have to be adjusted for inflation, supplemented with indirect costs, balanced with reduced costs, and then spread out over the 40-year lifecycle of the regulation. Finally, because the Department was undertaking a comprehensive benefit-cost analysis, the adjusted, supplemented and annualized costs of each requirement would have to be paired with an assessment of the corresponding benefits.

2.2 Requirements

Based upon its review of the Board’s final regulatory assessment for the 2004 ADAAG, the Department has determined the Final Rules will result in over 100 substantive changes to the 1991 Standards (Table 1 and Appendix 2). These changes are represented by two kinds of requirements – “supplemental” (or “new”) and “revised” requirements. The supplemental requirements are those that have no counterpart in the 1991 Standards and were initially adopted into ADAAG in the form of “supplemental guidelines” providing scoping and technical provisions for judicial, detention and correctional facilities (1998), play areas (2000), and recreation facilities (2002). While the supplemental requirements have been a part of the ADAAG since they were adopted, the Department is now adopting them into the ADA Standards for the first time. These requirements apply to elements and spaces that are typically found only in certain facility types, such as courthouses, jails, prisons, exercise facilities, sports and recreation facilities, recreational boating and fishing facilities, golf courses, miniature golf courses, amusement rides and playgrounds. (Some supplemental requirements, such as those relating to exercise facilities, swimming pools, and play areas, will apply to a broader range of facility types.) The Department has identified approximately 30 individual requirements from the supplemental guidelines that will represent substantive changes to the ADA Standards and are not currently being enforced.[8]

Revised requirements apply to elements or spaces that are currently either subject to (or specifically exempted from) a scoping or technical requirement in the 1991 Standards, and apply to the types of elements and spaces that are typically found in a wide range of commonly used facility types, such as restaurants, retail stores, schools, hospitals, and office buildings. Also the revised requirements apply to common building elements (such as windows) and commonly used facility types (such as residential dwelling units) that have long been subject to specific accessibility requirements, either through UFAS, another Federal accessibility standard (for example, under the Fair Housing Act or Section 504 of the Rehabilitation Act) or the International Building Code (IBC). All of the revised requirements were adopted by the Board in 2004 – rather than through earlier supplemental rulemaking – and all were described in the Board’s final regulatory assessment for the 2004 ADAAG.

This assessment defines revised requirements relative to the 1991 Standards as either “more stringent” or “less stringent”. Generally speaking, more stringent requirements are those that have been revised to require more accessibility than the current requirements, potentially conferring a greater benefit at a higher cost, while less stringent requirements are those that have been relaxed relative to the current requirement, potentially conferring a lesser benefit at a lower cost. For the most part, these categories correspond to the Board’s categories “no or minimal cost” and “increased cost,” on the one hand, and “reduced cost,” on the other. The difference in terminology is attributable to the difference between the two assessments: with respect to each requirement, the Board’s assessment measured only the costs, while the Department’s assessment has measured both the benefits and the costs.

The Department’s categories, however, do not track perfectly with those of the Board. Because the Board was assessing the cost impact of each requirement, first, against a baseline of the 1991 ADAAG (as amended through 2002), and secondly, as applied only to a select range of newly constructed and altered facility types, in cases where the 1991 Standards as interpreted and enforced by the Department requires more than the 1991 ADAAG (as amended through 2002), or where the nature of the revision has different cost implications for different types or sizes of facilities across the spectrum of facility types to which the requirement will apply, the Department has categorized the requirement differently. For example, the Department has determined that the revised requirements relating to public entrances (section 206.4.1 of the 2004 ADAAG), which the Board had determined would likely effect no change, may effect a change for certain very large facilities (not addressed in the Board’s assessment) for which the revised requirement may be less stringent than the current requirement. Likewise, the requirement relating to dwelling units with communication features (sections 809.5 and 708.4), which the Board had categorized as a more stringent requirement when costed against a baseline of UFAS, is being costed in this assessment against both UFAS (with respect to which it is more stringent) and an alternate baseline of the transient lodging provisions of the 1991 Standards, compared to which it is less stringent.[9]

Similarly, the revised requirement exempting parking spaces designated for the exclusive use of buses, delivery vehicles, law enforcement vehicles and the like (section 208.1, Exception), which the Board had identified as a “reduced cost” requirement, represents no change from the Department’s current interpretation of the 1991 Standards. However, because in revising the requirement the Board added a provision requiring parking lots containing such spaces, if they are accessed by the public, to provide an accessible loading zone, this requirement has been categorized as a “more stringent” requirement for purposes of this assessment. Similarly, due to differences between the Board’s interpretation of the 1991 ADAAG and the Department’s interpretation and enforcement of the 1991 Standards, other revised requirements that the Board had identified as imposing a “reduced cost” – including the revised scoping requirements for self-service storage facility spaces and washing machines and clothes dryers – have been categorized as “more stringent” requirements in this assessment.

In addition to the supplemental and revised requirements, the Department is also adopting in the Final Rules other regulatory requirements, including codifications of existing law, and requirements expected to have no cost impact. The codifications of existing law and the requirements expected to have no cost impact have not been incorporated into the Final RIA. 

Table 1 lists the revised and supplemental requirements from the Final Rules which have been included in this final regulatory analysis. A summary of these requirements is provided in Appendix 2, most requirements are assumed to apply to one or more facility groups. Allocation of requirements into facilities is discussed in Chapter 3.

Table 1 : List of Requirements

Requirements Modeled:

Requirements Without Significant Cost Implications And Not Modeled:

2.3 Facilities

The Final Rules adopt standards for new construction and alteration of facilities covered by Title II (which applies to state and local governments) and Title III (which applies to private entities operating commercial facilities or “public accommodations” as defined by the ADA). For purposes of the final regulatory analysis, public (Title II) and private (Title III) facilities are categorized separately. Table 2 lists the 68 facility groups or types assessed in the Final RIA.  Types of facilities include single purpose facilities such as hotels and classes of facilities such as retail stores (e.g. bakeries, laundromats) or service establishments (e.g. banks, dry cleaners). In some cases, facility groupings are defined based on the size of the facility (e.g. auditoriums and convention centers). Groups are also distinguished by economic characteristics, especially the responsiveness of average customers to changes in prices at facilities. For example, consumers would have less price responsiveness in buying gasoline than going to a restaurant because many people need to drive a car and because people can always cook at home. Finally, it must be noted that some facilities, such as play areas and pools may be elements in larger facilities, such as hotels. Benefits from using such elements are assumed to be conditional on facility use.

Table 2: List of Facilities

2.4 Structure of Analysis and Scenarios

2.4.1 Barrier Removal and Safe Harbor

To minimize the financial burden upon existing facilities, while still maintaining high levels of accessibility for persons with disabilities, the Department is adopting a safe harbor (SH) policy. Under SH, the Department will deem compliance with scoping and technical requirements in the 1991 Standards to constitute compliance with the ADA for purposes of meeting BR obligations under the Final Rules on an element-by-element basis. In other words, only elements in an existing covered facility which are in current compliance with the applicable scoping and technical requirements of the 1991 Standards will be eligible for SH.

Safe harbor will not, however, apply to certain requirements or facilities. First, safe harbor does not apply to supplemental requirements – such as the requirements covering play areas and recreational facilities – because such requirements necessarily have no counterpart in the 1991 Standards. Second, existing public facilities operated by State and local governments are not covered by this particular safe harbor provision because barrier removal obligations only arise under Title III. Existing Title II-covered facilities are instead subject to program access requirements. [10] Nonetheless, the Final Rules provide that elements in existing public (Title II) facilities that are already compliant with the 1991 Standards or UFAS, are not subject to retrofitting due solely to incremental changes reflected in these Rules.  This analysis thus assumes that Title II entities will not need to make changes to existing facilities except in the limited context of supplemental requirements applicable to public play areas, swimming pools, saunas and golf courses.

As the Department pointed out in the Advance Notice of Proposed Rulemaking (ANPRM), published on September 30, 2004:[11]

Several considerations support this approach. To the extent places of public accommodation have complied with the specific scoping and technical requirements of the current ADA Standards, it would be an inefficient use of resources to require them to retrofit simply to comply with the revised ADA Standards if the change provides only a minimal improvement in accessibility. In addition, covered entities would have a strong disincentive to comply voluntarily with the readily achievable barrier removal requirement if, every time the ADA Standards are revised, they are required once again to retrofit elements just to keep pace with the current standards.

Arguments against implementing SH include the possibility that some up-to-date technologies would not be implemented for barrier removal purposes. This could diminish accessibility for persons with disabilities. Although the reduced improvements compared to new facilities may be minor, some people may lose significant benefits by establishing SH.^[12]

2.4.2 Classification of Requirements

The framework for determining the impact of the Final Rules on the elements is illustrated in Figure 1. The framework focuses on elements, not facilities, because it is elements that are evaluated for compliance. Viewed another way, facilities are entirely composed of elements, some of which are subject to requirements. Facilities and elements both originate from the date the building is completed. They age, however, at different rates because each time an alteration is undertaken, elements are renewed. This framework classifies elements with respect to when they were built, the likelihood that a requirement will be readily achievable, and whether or not SH is adopted. This framework also illustrates the differences in how revised and supplemental requirements are modeled.

The number of existing elements that are subject to the 1991 Standards is divided into several groups to estimate the current level of compliance. Altered and newly constructed buildings are assumed to fully comply with the 1991 Standards.   Compliance with the 1991 Standards is also assumed for existing elements that: were built after 1993; altered after 1992; or have undergone barrier removal after 1992. Non-compliant elements are assumed not to have undergone retrofitting due to barrier removal that was not readily achievable. Classification of elements is as follows:

• The first division classifies elements as being in facilities designed and constructed for first occupancy before or after 1993. Facilities constructed after December 1992 are “new” compared to the 1991 Standards. [13]Figure 1 labels these conditions as “Built before 1993” and “Built after 1993”, respectively. The number of existing buildings constructed before 1993 is represented as the proportion (c).[14]
• The second classification then sub-divides elements in facilities constructed before 1993 into whether they have or have not been altered between 1992 and 2009.[15] The proportion of facilities altered is represented by the proportion (b).
• The third classification further sub-divides elements in unaltered facilities constructed before 1993 into whether barrier removal for these elements was or was not readily achievable. It is assumed that if barrier removal was readily achievable, then it already has been undertaken. This sub-classification applies to unaltered elements because, if they had been altered, they are assumed to already comply with the 1991 Standards. If barrier removal was not readily achievable, the element is assumed to not comply with the 1991 Standards. The proportion of unaltered elements for which it is assumed that barrier removal will be readily achievable under the Final Rules is represented by (a).

With respect to the revised, more stringent requirements in the Final Rules, existing elements comply through either barrier removal or alterations. In all cases, if barrier removal is not readily achievable, alterations are undertaken. Only compliant elements (relative to the 1991 Standards) subject to more stringent requirements are considered for barrier removal (under a hypothetical “no safe harbor” scenario in the Final Rules) and, of these, only elements for which it is assumed such retrofitting is readily achievable. For existing elements that are currently  not in compliance with the 1991 Standards due to barrier removal not being readily achievable, it is also assumed that  barrier removal would be similarly not readily achievable since more stringent requirements only increase the level of (and cost of) compliance.

SH policy determines which elements in existing unaltered facilities may forgo retrofitting to comply with more stringent requirements under the Final Rules. In particular, with SH, currently compliant elements (relative to the 1991 Standards) do not need to undertake barrier removal under the Final Rules and would only incur costs during an alteration. Without SH, all currently compliant elements (relative to the 1991 Standards) subject to more stringent requirements undertake barrier removal ahead of the alteration schedule if readily achievable. Implications of different SH policy are shown in Figure 1 in the columns W/ SH and W/O SH (with and without SH, respectively). Either BR (barrier removal) or Alt (alterations) are indicated and represent the type of cost and schedule necessary for compliance.

Elements subject to less stringent requirements already exceed compliance levels required by the Final Rules and thus have no further legal obligations under these Rules.[16] Of course, when elements subject to less stringent requirements are altered, which is assumed to eventually occur in the 40 year lifecycle of a building, such elements do incur alteration costs.

Evaluating supplemental requirements is straightforward. Supplemental requirements have no direct regulatory counterpart in the 1991 Standards. All existing elements must undertake barrier removal to comply with applicable supplemental requirements so long as readily achievable because the safe harbor does not apply to these requirements.  Supplemental requirements appear in Figure 1 as subject to requirements after 2010, when the Final Rules are expected to take effect. With or without a SH policy, existing elements subject to supplemental requirements are generally assumed to be noncompliant relative to the Final Rules, and, therefore, must undergo barrier removal to the extent readily achievable. This assumption may overestimate benefits and costs for these elements, as facilities may have attempted to make these elements accessible even in the absence of specific scoping and technical requirements in the 1991 Standards (by, for example, relying on accessibility standards provided in state or local building codes, or on the 2004 ADAAG guidelines published by the Board).

Figure 1 illustrates the conditions under which an element may become compliant and the associated cost. Boxes represent different conditions and arrows represent different pathways to these conditions. All arrows, except those dividing elements into new (supplemental), more and less stringent groups, correspond to proportions (or probabilities) of elements that fall under one of the conditions.

The percentage of elements that are readily achievable (a1) for the revised standards may be equal or proportional to a facility’s original readily achievable status (a). This proportion is not known for facilities or elements. Accordingly, the actual level of readily achievable is modeled as a specific level in several scenarios. Differences in results between these levels are compared to illustrate the range of potential impacts depending on the actual state of compliance and ability to readily achieve barrier removal.

The product of these probabilities represents the distinct likelihood that such a condition would occur. For example, an element existing before 1993, altered after 1992, subject to a more stringent requirement, and is readily achievable has a probability of occurring equal to: (c?b?a1). The sum of all products of probabilities associated with more (or less) stringent requirements is the total proportion of elements that apply to a particular cost schedule W/ SH or W/O SH. These two cost schedules differ with respect to the unit costs necessary to bring an element into compliance. For example, as stated above, more stringent requirements that are readily achievable would incur alterations costs under a SH scenario; the costs would be barrier removal if SH was not adopted.

Figure 1 : Diagram of Conditions Corresponding to Compliance of Elements

2.4.3 Alternative Baselines

The 1991 Standards are the primary baseline for this assessment because they are the only uniform set of accessibility standards that apply to every place of public accommodation, commercial facility and State or local government facility in the country.[17]  While most States and/or local jurisdictions have enacted building or accessibility codes that adopt IBC/ANSI model codes (or provisions therein) that mirror requirements in the Final Rules, there is wide variation with respect to which standards have been adopted by such jurisdictions.  Because the model codes are voluntary, public entities often modify or carve out particular standards when adopting them into their laws.  Across 90,000 towns, cities and counties, the result is a patchwork of different accessibility requirements providing varying levels of access. By contrast, because the ADA is a mandatory Federal law, it applies the same standards to every facility in the country, ensuring a uniform level of accessibility nationwide.

Although the 1991 Standards serve as the primary baseline for this final regulatory assessment, the analysis nonetheless recognizes the influence of State and local law on the accessibility requirements that would apply to facilities even if the Department were to elect not to adopt the Final Rules. A version of the IBC has been adopted, in whole or in part, at the state or local level in all 50 states and the District of Columbia.[18]   Many IBC provisions are equivalent in the Final Rules; indeed, code harmonization was one of the Access Board’s central goals when promulgating the 2004 ADAAG.  Thus, when the Final Rules become effective, facilities that are subject to a building code that incorporates IBC or ANSI standards that mirror requirements in the Final Rules will experience less impact from the Department’s adoption of these Rules than other facilities.

In its regulatory assessment for the 2004 ADAAG, the Board presented its cost results as a range encompassing three baselines – current ADAAG, IBC 2000 and IBC 2003 – and discussed the extent to which State and local governments have adopted the model codes. As the Board observed, however, some jurisdictions that adopt the IBC either amend it or adopt separate accessibility codes. Several States that have adopted the IBC have either carved out Chapter 11 (which provides the scoping requirements for accessible facilities), have not adopted the referenced American National Standards Institute (ANSI) requirements (which provide the technical standards for accessible facilities), or, even where they have adopted ANSI, specifically permit facilities to comply with either ANSI or ADAAG. It is also not necessarily self-evident from IBC adoption whether a particular State or local jurisdiction also adopted the supplemental accessibility provisions provided in Appendix E, which must be affirmatively adopted to be effective. Therefore, the mere fact that a State or local government has adopted a version of the IBC or ANSI model code does not necessarily mean (absent additional research) that all facilities in that jurisdiction are legally subject to its every chapter, appendix, or provision therein.

The Department had considered following a state-by-state approach in which the relevant baseline for newly constructed and altered facilities would be locality dependent.  However, given the many variations among State and local building and accessibility codes with respect to IBC/ANSI adoption, it was determined that it would be technically infeasible (from a modeling perspective) and inordinately time-consuming to research and construct state- and locality-specific baselines for the over 100 requirements and across the over 60 facility groups covered by this final regulatory assessment. Therefore, the Final RIA presents benefits and costs for newly constructed facilities, altered facilities and existing facilities nationwide as measured against four “uniform” baselines – the primary baseline of the 1991 Standards, and three alternate baselines: IBC 2000, IBC 2003 and IBC 2006 – in each case assuming that the baseline applies to all facilities nationwide.  With respect to each of these latter three IBC baselines, it is assumed that all of the relevant provisions of ANSI, Chapter 11 and Appendix E also apply. This assumption is necessary because these are the sources of many of the accessibility standards that apply under the IBC. If none of these sources were assumed to apply, an entity’s adoption of the IBC would afford an incomplete picture of the accessibility of its facilities, and if some but not all of them were assumed to apply, predicting which baselines would apply to which facilities would be impossible. While this approach does not break the results of the assessment down state-by-state, it does permit facilities in each State to see how the impact of the Final Rules varies depending on which version of the IBC the State or local authority has adopted or might adopt in the future.

Additionally, to further assist stakeholders, the Final RIA also includes a more limited set of requirement-specific and state-specific alternate IBC/ANSI baselines for a subset of 20 requirements that have readily identifiable equivalent IBC or ANSI counterparts and that generally have negative NPVs under the primary baseline scenario. These alternate IBC/ANSI baselines are used in order to demonstrate the likely actual incremental impact of these requirements under current conditions nationwide.  While time-consuming, it is possible through research to determine with relative certainty the extent to which state or local jurisdictions have adopted particular IBC or ANSI provisions. However, there is no publicly available “facility census” to provide information concerning the location, age, and type of facilities nationwide. Thus, in order to construct requirement-specific and state-specific IBC/ANSI baselines, it was necessary to develop proxies with respect to the number and location of facilities in each facility group. For purposes of these alternate IBC/ANSI baselines, it is assumed that the number of facilities in each facility group that are located in any particular State or local jurisdiction is equal to the percentage of the current United States population (based on statistics from the U.S. Census Bureau) residing in that jurisdiction. The results of these analyses using requirement-specific and state-specific alternate IBC/ANSI baselines are presented in Section 6.2.2.       

Baselines are applied in the model on a per-requirement basis. As such, even within an alternate IBC baseline scenario, where the current requirement in the 1991 Standards is more stringent than the IBC provision, the current requirement trumps the IBC provision and continues to serve as the relevant baseline with respect to that requirement. The reasoning behind this methodology is that the 1991 Standards are Federal law, and under the Supremacy Clause of the U.S. Constitution, where a Federal standard conflicts with a State or local standard, the Federal standard prevails. The ADA permits State or local building codes to provide for greater accessibility than the ADA Standards, but not less. Therefore, in each of the four alternate baseline scenarios, with respect to each new or revised requirement, the IBC provision is only used as the baseline where it is more stringent than the current requirement in the ADA Standards. As a practical matter, this is more frequently the case with respect to the “more stringent” requirements, which were harmonized upward (that is, the requirement stated in the 1991 Standards is less stringent than the IBC provision, and has now been strengthened). By contrast, because most of the “less stringent” requirements are those where the current requirement has been harmonized downward (that is, the requirement stated in the 1991 Standards is more stringent standard than the IBC provision, and has now been relaxed), they have been assessed against the default baseline of the 1991 Standards.

2.4.4 Summary of Scenarios

Several dimensions of uncertainty in how the Final Rules apply to actual facilities are captured as independent scenarios.[19]These dimensions include: readily achievable levels [0%, 50%, 100%], baselines [1991 Standards, IBC 2000, IBC 2003, IBC 2006], and safe harbor [SH versus NSH].  These varying dimensions are shown in Chapter 6.