Determination of a concrete or asphalt pavement section is important to the schematic and preliminary design of a roundabout due to the subsequent performance checks for fastest path and design vehicles. Determining whether the roadway will have a monolithic curb, or a separate curb and gutter section may have a direct impact on the curb offset location and the subsequent performance checks performed for a roundabout.

For constructability and grade control, setting up additional alignments and profiles of the edge of pavement produces optimal grade control for retrofit designs. Developing a grading surface that closely follows existing topography or the natural grade of the intersection often results in a tilted plane, also known as “tipping the circle”. Tipping the circle requires gradual transition from sloping in on the high side to sloping out on the low side. The preferred maximum cross-slope of the low side should be 2-percent to prevent truck roll-overs.

Additional considerations for the proper accommodation of OSOWs may be needed for vertical clearance checks of lowboys and other vehicles that have a reduced vertical envelope. In rare cases, the height of the center island truck apron and the circulatory grade may need to factor into the check vehicle vertical clearance.

For additional guidance, refer to , Chapter 11.

Ideally, drainage structures will be installed outside of the limits of the ICD of a roundabout. Inlets upstream of crosswalks in advance of a roundabout and downstream of the ICD typically provide enough capture from runoff within the footprint of a roundabout. Minimum and maximum slopes should be analyzed, including a typical cross slope within the circulatory roadway of 1.5 percent to 3.0 percent. Chapter 10 of provides guidance on drainage best practices and examples.

Pavement marking plans should be separated from signing plans for clarity. Legends are encouraged on pavement marking sheets to convey the TxDOT bid item numbers and an accurate description of the bid item, including color, width, length, and gap length of the pavement marking.

to represent TxDOT’s preferred pavement markings for roundabouts. , Chapter 12 contains supplemental information regarding pavement markings at roundabouts. The also serves as a resource in preparing pavement marking designs. Key considerations for pavement markings at roundabouts consist of:

The most current version of the must be sourced for providing signage at roundabouts. Key considerations for signage at roundabouts include:

Advance overhead lane assignment signage on multilane roundabouts is strongly recommended for wayfinding and driver recognition, especially at interchange roundabouts and roundabouts that are located near other alternative intersections, interstate access points, or where more than two lanes may exist along the approach to a roundabout. Exhibit 12.8 of provides an example of the preferred lane assignment sign assembly and placement for a two-lane roundabout.

, Sections 14.1, 14.2 and 14.3 focus on illumination considerations, lighting levels, and illumination equipment type and location. Since agency illumination policies vary widely across the State, it is important to factor in local restrictions or requirements such as Dark Sky Initiatives.

Section 14.4 of provides guidance for roundabout landscaping. Key considerations for landscaping include:

For roundabout installations where an existing intersection is being reconstructed or modified to accommodate a roundabout, attention to a few factors that influence how the roundabout will be constructed is important. Common considerations consist of:

Oftentimes opposing directions will be narrowly separated by a double-yellow pavement marking. If routing bi-directional traffic through a portion of a constructed multilane roundabout, additional width may be needed to accommodate the swept path of an articulated truck or front/rear overhang of an extended vehicle.

For concrete pavement roundabouts, a jointing plan is commonly prepared by the engineer-of-record or supplied by the contractor. Multilane roundabouts should have panels and joint lines such that a pinwheel pattern is developed to favor yielding of entering traffic and priority to existing traffic. Joint and panel patterns must not contradict lane divisions and pavement markings. The optimal jointing plan reveals where lane divisions are and where vehicles circulating can exit a roundabout without changing lanes.

Exhibit 13.8 of and show the use of a pinwheel pattern jointing plan. Joints must also be installed using conventional minimum and maximum panel sizes. Utility appurtenances, such as manholes, water valves, and curb inlets, should be accounted for in jointing techniques, to minimize cracking and failure of adjacent concrete pavement.

For roundabouts built under traffic conditions, the jointing plan must factor in the location of construction joints based on the phased construction of the roadway. Construction phasing considerations may result in a deviation from a standard jointing pattern, however, the proposed jointing strategy should place longitudinal and transverse joints as close as possible to a jointing design that would be produced in lieu of phased construction.

Bicycle ramps can be beneficial at single-lane roundabouts and are commonly considered at multilane roundabouts where on-street bicycle activity exists or is anticipated. , Exhibit 10.25 and Exhibit 10.26 show an example of how bikes can transition from the on-street facility to the parkway facility and from the parkway facility to the on-street facility.

Based on the publication, multilane pedestrian crossings at roundabouts and channelized turn lanes must have additional treatments that alert motorists to the presence of pedestrians or slow or stop traffic at those crosswalks. Additional treatments can consist of raised crosswalks, pedestrian actuated rectangular rapid flashing beacons (RRFB), pedestrian hybrid beacons (PHB), or a traffic control signal with a pedestrian signal head (R306.4.2).

The August 2023 Rules and Regulations update included additional clarification and guidance for pedestrian facilities consisting of: