Construction Management

Posted: August 27th, 2021

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Construction Management

The paper aims to detail construction management work for single land roundabout and mini-roundabout. The work in the paper is informed by the need to construct a roundabout at the intersection of New Meridian and Pitkin that will accommodate bicycle and pedestrian movements. This follows an established design for the two preferred roundabouts as illustrated in figures 1 and 2 below;

Figure 1: Single Lane Roundabout

Figure 1 is a single integrated-roundabout. The first green circle is a bike lane, and the second one is a pedestrian walk. Both are outside the roundabout circle.

Figure 2: Single-Lane-Integrated Combine Roundabout

Figure 2 shows an integrated combined roundabout with a bike lane inside the roundabout. Accordingly, basic guidelines apply to the construction of single-lane roundabouts. First, a splitter island must be provided on all the lanes of a single roundabout to provide pedestrians’ refuge. They also assist in the control and guiding of traffic coming and getting out of the roundabout. Secondly, it should be provided with an average entry of 16 feet, usually flared from the upstream approach widths (CDOT Roundabout Design). In unavoidable circumstances, an entry width value lower or higher would be appropriate depending on the site. Other provisions include circulatory roadway width, central island, and truck apron, designed with a single entry curb radius that should be typically adequate. Equally, to minimize the chances of congestion and possible crashes, exit radii should be larger than entry curb radii. However, this should be balanced by proper measures to restrict speed levels at the roundabout. It is also advisable to have right-turn bypass lanes, which are notable for the increased life of a roundabout CDOT (Roundabout Design). This is because they help remove traffic congestions within the roundabout, thus ensuring more robust performance.

Besides, single roundabouts have some advantages. These roundabouts offer more excellent safety to pedestrians and cyclists since they lower the speed and eliminate unnecessary left turns. This is enhanced by increased traffic flow and a single direction movement (City of San Diego Official Website). However, they pose some challenges, including the possibility of increased queuing, especially during peak times. Besides, they are likely to encourage high speeds due to large diameter, supported with diversions from cyclists and pedestrians desire lines (City of San Diego Official Website; “Roundabouts Are Not a Silver Bullet | MikeOnTraffic Blog.”). Thus, besides being useful in enhancing traffic flow, these challenges restrict the single-lane roundabouts’ capacity to improve traffic flow.

Mini-Roundabouts

These are small-single lane roundabouts designed with full traversable central island utilized for low-speed. They are suitable for urban environments as they encourage an average speed of 30 miles per hour or below (CSU Construction Standards). Regarding construction management, these roundabouts should be designed as expansive as possible, particularly at the intersection. For instance, the inscribed diameter should be designed about 90 feet (CSU Construction Standards). This allows accessible accommodation of design vehicles that navigate a raised island. Besides, splitter islands should be designed to help align vehicles and support appropriate circulation and enhance pedestrian refuge. Equally, pedestrian crosswalks and ramps should be located next to curb returns at intersection corners. It is recommended that crosswalks be located at least 20 feet upstream of the entrance line (CSU Construction Standards; City of San Diego Official Website). Here, it is possible to accommodate a single vehicle stopping at the crosswalk or the entrance line. Subsequently, they should be constructed to have an outward draining at the outer side of the intersection City of (San Diego Official Website). Therefore, this will ensure maximum visibility for the users.

Consequently, mini-roundabouts have some advantages. They have a small footprint that allows them to properly fit within an existing right-of-way besides improving pedestrians’ traffic flow and reduced crashes. However, they exhibit surmountable challenges, such as limiting the possibility of providing adequate close pedestrian crossing (“Roundabouts Are Not a Silver Bullet | MikeOnTraffic Blog.”.) Also, it may pose difficulties to cyclists negotiating around the mini-roundabout. Thus, these challenges limit their operational efficiency. 

Works Cited

“Roundabouts Are Not a Silver Bullet | MikeOnTraffic Blog.” Mike on traffic, 23 Aug. 2016, www.mikeontraffic.com/roundabouts-not-silver-bullet/.

City of San Diego Official Website, www.sandiego.gov/sites/default/files/legacy/planning/programs/transportation/pdf/roundabout.pdf.

CDOT Roundabout Design, Chapter 19. Accessed 25 Oct. 2020 fromhttps://www.codot.gov/business/designsupport/bulletins_manuals/cdot-roadway-design-guide-2018/dg18-ch19

CSU Construction Standards. Accessed 25 Oct. 2020 from https://www.fm.colostate.edu/constr_standards