Traffic

This presentation pertains to Transportation Research Synthesis TRS 1206, Traffic Forecasting on Trunk Highways in Nonmetropolitan Areas: A Survey of State Practice.

A literature search and a survey of snowbelt states showed that the problem was not unique to Minnesota. Induction loop failures were caused by moisture, loop sealant deterioration, pavement cracks, etc. Mn/DOT personnel were observed making loop repairs and contract installations were also reviewed. No one item appeared to be the prevalent cause for failures. The study results recommend development of a strict set of installation standards using the most effective techniques; thereafter, review and thorough investigation of all failures of new installations. Causes for failures will be pinpointed and development of proper remedies for these failures will result.

This study was conducted to develop a rational method for selecting the most appropriate type of traffic control at construction sites involving the closing of a one-lane bridge. The study consisted of a literature review, a survey of practices in other states, the observation of a number of actual construction sites, the collection and analysis of data from these construction sites and finally, the development of methods for estimating the capacity and measuring the effectiveness of various types of traffic control. As a result, a method for selecting an appropriate type of traffic was developed. This method takes into account variables such as sight distance, bridge length, traffic volumes and capacity, consideration of the costs and benefits of various types of control and an analysis of the geometric features of the geometric features of the approaches to the bridge.

This document constitutes the areawide TOPICS Plan for the City of Rochester, Minnesota, which has been developed under the Federal program called, "Urban Traffic Operations Program to Increase Capacity and Safety (TOPICS)." The report has been prepared in accordance with the Federal Highway Administration's Policy and Procedure Memorandum 21-18, dated May 13, 1971, which governs the expenditure of Federal Aid highway funds for the TOPICS Program.

This traffic survey was created as part of a planned improvement of U.S. Highway 52 between St. Cloud, Minnesota and Sauk Center, Minnesota.

This research developed an online procedure to estimate the weaving capacity through time for a simple ramp-weave section, the most common type of weaving areas in the Twin Cities' freeway network. The field observations and the analysis of the traffic data collected from a sample weaving section indicate that the freeway-to-ramp and ramp-to-freeway vehicles first merge and travel together at the beginning portion of the auxiliary lane before they split to the mainline or exit ramp. The length of the shared portion of the auxiliary lane, called an "effective weaving zone," varied depending on the length of an auxiliary lane and the amount of weaving volume. The above merge-split behavior and the resulting mixed flow on the auxiliary lane for a short time period explains the fact that the maximum possible weaving volume in a simple ramp-weave section equals the maximum through volume that the auxiliary lane can handle. Researchers used a Kalman Filter to obtain estimated weaving volume data from three weaving, which supported this observation. Based on the above findings, an online procedure was developed to estimate the maximum possible weaving volume for a given ramp-weave area through time using the volume and occupancy measurements from the loop detectors. The proposed procedure assumes that the maximum possible weaving volume for a given time interval is a function of downstream traffic conditions that can be quantified by estimating the time-variant merging and diverging capacities of a given weaving section. Test results with the five-minute data from a ramp-weave site indicate that the maximum possible weaving volume can be estimated with reasonable accuracy during congested peak periods.

The annual Congestion Study is a geographical illustration of the metropolitan freeway system's traffic performance. It portrays time and areas of congested traffic flow during the A.M. and P .M. peak periods. Congested areas are determined from data gathered by traffic management sensor arrays. The data, five-minute volumes and lane occupancy values, provide input into the determination of the average five-minute running speeds per lane. This report is a summary of the time a freeway operates below 45 miles per hour. Freeway system field observations indicate that under this condition, shock waves develop in the traffic flow. Our working definition of congestion is then traffic flow below 45 miles per hour. The data summary compares the traffic during the month of October in each of the years. This is done to minimize the effects of construction and maintenance-induced congestion and to account for school-induced traffic loads. The study uses 1993 as a base year, the first year the report was done.

Traffic centers gather information from traffic sensors at regular intervals, but storing the data for future analysis becomes an issue. This report details work to improve the speed and effectiveness of traffic databases. In this project phase, researchers redesigned the data model based on the previous phase's data model and decreased the storage requirements by one-third. Researchers developed a web-based Graphical User Interface (GUI) for users to specify the query of interest; the outcome of the performance tuning gave users reasonable response time. The beneficiaries of this effective database would include the driving public, traffic engineers, and researchers, who are generally not familiar with the query language used in the database management system. This report summarizes the detailed reference, such as benchmark query, sample data, table schema, conversion code, and other information.

Transportation agencies increasingly emphasize access management programs as a cost-effective way of achieving improved safety and capacity on roadways, improved aesthetics and air quality, and better coordination of transportation and land development. This paper presents a summary of access management goals, regulatory/policy approaches, and successes/conclusions of other states and countries. States take a range of different regulatory approaches to access management. Colorado, Florida, and New Jersey have state access management codes. Legal codes provide predictability and consistency statewide, but are regularly challenged in court. Some agencies use administrative rules, or state policies or guidelines, but share access authority with local municipalities. In cases where authority rests with local officials, a strong need exists for communication, education, and involvement of state and local officials, planning organizations, developers, and landowners to achieve consistent results. There is a high level of agreement that managing the location, design, and operation of driveways, median openings, and street connections to a roadway can reduce accidents, improve traffic flow, and discourage strip development. The effects of access management on business vitality and economic development have not yet been as extensively studied.

This report looks at the effectiveness of microloops as replacements for the inductive loops that are used as advance detection sensors at actuated signalized intersections. It also evaluated whether different loop detector models from several manufacturers can operate satisfactorily and consistently when attached to the microloop, and also determined the performance accuracy of loop detectors attached to a one-probe microloop or to a two-probe microloop. Research results support the hypothesis that microloops can function as a reliable replacement for inductive loops in advance detection applications. To achieve optimum results, the microloops must be used with Canoga C800 series vehicle detectors with version 1.2 firmware as part of a matched component system. Different brands of detector amplifiers do not perform as satisfactorily with the M701 microloop. Only the detectors that incorporate algorithms specifically developed for use with microloops demonstrated a performance that approaches the performance of inductive loops. These detectors also can be used in Presence Mode, thus allowing the traffic engineer to use the microloop in a broad range of applications. The strong attributes of microloop-based traffic sensors include shorter installation time, less pavement invasion, and improved life-cycle costs compared to traditional saw cut inductive loops, while providing consistent and accurate performance under all environmental and road conditions.