4.2.2 Design Criteria and Controls

The design criteria and controls to be used on the project are established and documented in the DSR at the beginning of project development. The design criteria to be used is determined by the type of construction that is proposed and other selection considerations including:

Whether the project is on the Federal National Highway System (NHS), State Highway System, or off-system roadway;

Whether the project is or needs access control (i.e., conventional or access-controlled facility);

Functional classification of the roadway (i.e., freeway, arterial, collector, or local);

Context classification of the roadway (i.e., rural, rural town, suburban, urban, or urban core);

Terrain classification of the roadway (i.e., level, rolling, or mountainous);

Traffic characteristics of the roadway (e.g., current/projected Average Daily Traffic (ADT), operations, safety); and

Funding category of the project (certain funding categories pertain to specific design criteria).

Table 4-1

gives definitions of the different highway construction categories.

Table 4-1: Highway Construction Category Definitions
Highway Construction Category	Definition
Resurfacing	Limited existing pavement surface repairs such as milling, spot patching, seal coat, rut repair, crack sealing, and fog sealing.
Restoration	Existing pavement structure repairs such as patching or rebuilding short sections of road, hot mix overlays, shoulder edge repairs, or minor safety improvements (i.e., guardfence, pipe headwalls, etc.).
Rehabilitation	Partial or full depth pavement reconstruction on existing profile/alignment such as removal and replacement of the existing riding surface and base material, driveway improvements, ditch regrading or safety improvements (i.e., guardfence, pipe headwalls, etc.). If approved, minor lane/shoulder widening, adding medians/curbing, minor improved drainage design or intersection improvements are included.
Reconstruction	Projects that utilize an existing roadway alignment (or make only minor changes to an existing alignment) but involve a change in the basic roadway type. Changes in the basic roadway type include widening a road to provide additional through lanes or adding a raised or depressed median where none currently exists, and where these changes cannot be accomplished within the existing roadway width (including shoulders).
New Construction	Projects on a new alignment or new construction.

The applicable design criteria are based on construction type is shown in

Table 4-2

. Additional categories of design criteria are discussed in the RDM and in

Table 4-3

Table 4-2: TxDOT Construction Types and Applicable Design Criteria
Roadway Design Criteria	Highway Construction Categories	Definition
2R	Resurfacing and Restoration	Projects consist of non-freeway work on facilities not on the National Highway System (NHS) with a current ADT ≤ 2500 per lane that propose to restore the pavement to its original condition. Includes restoration of pavement structure, ride quality, or other necessary components to its existing cross section configuration. The principal purposes of these projects are surfacing and repair of the pavement structure. The addition of continuous two-way left-turn lanes (TWLTL), acceleration/deceleration lanes, turning lanes, and shoulders are acceptable as restoration work as long as the existing through lane and shoulder widths are maintained as a minimum. Work DOES NOT include the addition of through travel lanes.
3R	Resurfacing, Restoration and Rehabilitation	Projects consist of transportation projects that extend the service life and enhance the safety of a roadway including freeways and NHS roadways. In addition to the work described under resurfacing and restoration, the activities include upgrading the geometric design and safety of the facility. Work may include the upgrading of geometric features such as roadway widening, minor horizontal and vertical realignment (typically less than 10% of the project length) and improving bridges to meet current standards for structural loading and to accommodate the approach roadway width. Work DOES NOT include the addition of through travel lanes.
4R	Resurfacing, Restoration, Rehabilitation, and Reconstruction and New Construction	Projects on a new alignment or new construction. Projects that upgrade an existing roadway to meet geometric criteria for a new facility. Projects that include substantial changes in the geometric character of the highway, such as widening to provide additional through lanes, significant horizontal or vertical realignments, and major improvements to the pavement structure to improve long term service. Bridge replacement projects with ADT > 400.
5R	Mobility Corridors	Projects that are intended to regenerate, or produce new, long-term transportation opportunities including multiple modes such as rail, utilities, freight, and passenger characteristics.

The appropriate design criteria for the construction type are chosen according to guidance found in the RDM based on the functional and context classification of the roadway. Refer to Chapters 1 – 12 of the RDM for more guidance on the selection of the applicable design criteria.

Design controls that are established according to the selected design standards include:

Design loading structural capacity;

Context classification;

Design speed;

Capacity and Level of Service (LOS);

Project traffic;

Environmental constraints (e.g., public parks, historic and cultural features, displacements, wetlands, and floodplains);

Design vehicle;

Pedestrian and bicycle requirements;

Physical constraints (e.g., existing ROW, approach roads, railroads, and major utilities);

Type of stormwater facilities;

Navigation requirements; and

High water requirements.

Table 4-3: Other Construction Types and Applicable Design Criteria
Roadway Design Criteria		Definition	Reference
PM	Preventative Maintenance	Projects with work to preserve, rather than improve, the structural integrity of the pavement and/or structure. Includes ACP overlays (maximum 2” thick); seal coats; cleaning and sealing joints and cracks; patching concrete pavement; milling or bituminous level-up, shoulder repair; micro-surfacing; scour countermeasures; restoring drainage systems, cleaning and painting steel members to include application of other coatings, cleaning and sealing bridge joints, bridge deck protection, cleaning and resetting bearings, cleaning rebar/strand, and patching structural concrete.	Maintenance Management Manual and Maintenance Operations Manual
5R	Mobility Corridors	Projects that are intended to regenerate, or produce new, long-term transportation opportunities including multiple modes such as rail, utilities, freight, and passenger characteristics.	Roadway Design Manual
Special Facilities	Highway Safety Improvement Program (HSIP)	Projects involving highway safety improvements including medians, turn lanes, intersections, traffic signals, and rumble strips. Projects must align with the emphasis areas in the Texas Strategic Highway Safety Plan (SHSP) such as roadway and lane departures, intersections, older road users, and pedestrian safety.	Highway Safety Improvement Program Guidelines
	Off-System Bridge Replacement & Rehabilitation	Projects that are included in the off-system bridge replacement and rehabilitation program; the facility is not likely to be added to the designated state highway system; and has a current ADT of 400 or less. High-volume (current ADT > 400) off-system bridge replacement and rehabilitation projects should use the appropriate 3R or 4R criteria.	Roadway Design Manual
	Historically Significant Bridges	Projects that contain a designated historically significant bridge.	Historic Bridge Manual
	Texas Parks and Wildlife Department (TPWD)	Projects that include work on Park Roads (PR) and Wildlife Roads (PW). This includes constructing, repairing and maintaining roads in and adjacent to state parks, state fish hatcheries, state wildlife management areas and their support facilities.	Texas Parks and Wildlife Department Design Standards for Roads and Parking

4.2 Preliminary Design Concept Conference