Archive for the ‘Roadway’ Category

Urban Mini Roundabouts Replace 96 Conflict Points

This unique project utilized medians and fully mountable mini roundabouts in an essential urban corridor to improve safety while minimizing right-of-way impacts for the City of Columbus.

HISTORY

In the 1970s, the SR 161 corridor was widened and improved to its current configuration. SR 161 is a rapidly developing area, so to safely handle its projected traffic, improvements included modern ideas in access management, including medians and service roads close to mainline SR 161. The service road intersections along the SR 161 corridor are only separated by 60-70 feet, far short of the 300’ separation recommended by the National Cooperative Highway Research Program. The pair of service road intersections, in addition to the SR 161 intersection, created three closely spaced intersections with 96 total vehicular conflict points. As this area continued to develop, it became obvious that increasing traffic and service road intersections too close to SR 161 created a safety concern. Because of these safety concerns, the City of Columbus selected DLZ to prepare a corridor study, the State Route 161 Corridor Study (PID 97169). This study helped produce six short-term improvements and four long-term alternatives.

ALTERNATIVES

The short-term alternatives included an education plan, an enforcement zone, minor signal modifications, and ‘do not block the box’ intersection signs. One other constructed, short-term alternative included placing a queue cutter traffic signal at the end of the service road. This traffic signal provided a red light at the intersection of the Service Road with Cleveland Avenue to allow traffic entering Cleveland Avenue to cut across four lanes of traffic stopped by this signal and safely enter the southbound left turn lane. The long-term alternatives for the study included maintaining two-way operation on service roads with medians and mini roundabouts, relocating the service road intersections further from SR 161, placing cul-de-sacs at the end of the Service Roads, placing mid-block right in/right out for access, and removing left turn lanes and installing mid-block r-cuts.

PREFERRED ALTERNATIVE

Based on the study’s results and feedback from stakeholders and the public, the preferred long-term alternative was to maintain 2-way operation on the service roads with medians on the side streets and mini-roundabouts to drastically decrease conflict points. Maple Canyon Avenue was selected to improve first because of its #3 ranking on the Mid-Ohio Regional Planning Commission’s (MORPC) yearly “Top 40 Regional High Crash Locations” list.

WHY USE MINI ROUNDABOUTS

Using traditional roundabouts in this highly developed urban area would damage property significantly. With these being the first mini roundabouts designed in the City of Columbus, DLZ visited numerous mini roundabouts in Ohio and Michigan to observe their performance, evaluating many sizes of mini roundabouts, from 70’ ICD (Inscribed Circle Diameter) to 100’ ICD. Many design vehicles like passenger cars, semi-trucks, school buses, delivery trucks, and fire trucks were also evaluated, and to balance improved traffic operations with property impacts, Columbus selected a 90’ ICD. Columbus laid out this design in a parking lot and drove fire trucks and garbage trucks through the layout to ensure this mini-roundabout concept could accommodate the different vehicles. Medians were meticulously placed through the side streets to prevent through and left-turning movements. DLZ performed a queuing analysis to ensure traffic waiting at the SR 161 traffic signals would not back up into the mini roundabout. This location also includes the new Columbus Fire Station. A signal pre-emption for the SR 161 traffic signal was provided, as well as a depressed median with stamped concrete to allow emergency vehicles to turn left toward SR 161 across the median.

OTHER FEATURES

This project also included decorative, gray-stamped concrete, mainline SR 161 signal improvements, a shared-use path, storm sewer improvements, signal improvements, sidewalks, water improvements, street lighting, and BMPs including Silva Cells, oversized pipes, and bioretention swales.

COLUMBUS’ OVERALL VISION

This mini roundabout solution will eventually be constructed at seven sets of intersections along the SR 161 corridor. Construction was completed on Maple Canyon Avenue in September 2023, and this project has improved the corridor’s safety and traffic operations. Construction is underway or completed for three other mini roundabouts within the State Route 161 Corridor Study, and design is ongoing to place roundabouts at the remaining intersections.

Traffic Data Collection: Keys to a Successful Roadway Project

Accurate data collection can greatly impact the success of a roadway project. For three decades, DLZ has contributed to the vast array of traffic data utilized by public agencies from the local to federal level in the planning and analysis of our transportation networks. While DLZ has stayed at the forefront by incorporating cutting edge technologies for collecting accurate vehicular, bicycle, and pedestrian data safely and efficiently, we are constantly exploring new opportunities to provide our clients with more accurate and reliable data.

Historically, pneumatic road tubes have been utilized for 24-hour or longer roadway segment counts to collect volume and classification data. We’ve used count boards and field staff to manually collect classified turning movements at intersections and pedestrian and bicycle data. These methods are still used and are often the best alternative for a given situation. However, newer technologies have become available that improve accuracy and reliability of data collection while minimizing staff exposure to live traffic conditions during installation and removal of equipment. Magnetic lane counters like MHCorbin’s NC350 units collect length based classification in each lane of a roadway and can be secured in each lane quicker than road tube setups needed to collect comparable directional, classification data. NC350’s can also be a more reliable option in situations where tubes may become unsecured over the course of a count period. Video collection systems such as Miovision’s Scout Units can be used to collect turning movement counts, bike and pedestrian data at intersections and roadway segment counts as well. Video units are installed on the side of the road eliminating the need for technicians to enter or cross travel lanes as is needed for installing tubes or magnetic lane counters.

Efficiency Matters
DLZ collects traffic data at 3,000 to 5,000 locations each year and it has become increasingly important to streamline the firm’s processes for scheduling field crews, documenting location and device information in the field and tracking progress in the office. To this end, DLZ has incorporated ESRI’s family of ArcGIS desktop, web and mobile applications into our traffic data collection workflow. Traffic Engineers in the office develop schedules for field crews marking locations to be collected in ArcGIS and synced with ArcGIS Online. DLZ field staff utilize ESRI’s Collector app on their iPads to see their scheduled locations and can use the Navigator app to find efficient travel times between locations. Field notes that are needed to identify the counter used and its placement are entered in Collector along with geocoded pictures of the installation. This information is synched with ArcGIS Online and used in preparing data reports without the need to transcribe handwritten paper notes in the office. Incorporating ArcGIS into a firm’s data collection processes greatly improves efficiency and reduces errors that might require recounting a location.

Safety First
Safely collecting traffic data begins with the employees. DLZ’s field staff, many of whom have been with the company for 10 or more years, focus on safely installing and removing equipment within or on the side of roadways and are properly trained to do so. Having a fleet of conspicuous work trucks with flashing lights, advance warning signs and cones for use as needed are all important safety measures to consider. All DLZ field staff wear reflective clothing and are certified in setting up and conducting flagging operations. However, every effort is made to minimize the time spent at each location. Closing a traffic lane is rarely needed.

Transportation agencies depend on current, reliable traffic data in order to make important maintenance and capital improvement decisions for their roadways. Traffic data is also a key aspect of funding requests for federal and state transportation maintenance and improvement programs. Ultimately, the quality of the transportation system serving our communities depends on accurate traffic data collected safely and efficiently.