This report presents the results of a review of long held contentions regarding driver choice of speed and reaction to speed limits. Areas of concern that were studied included influence of the roadway environment, reaction to school speed zones and reaction to warning flashers. Results of the review show that drivers do vary their speed under differing conditions, they do not react as desired to lowered speed limits or to passive signing. They do lower speeds when they see a warning flasher in conjunction with limit signs, but not as much as is requested. There was evidence too that in some zones a lower limit may result In a more hazardous situation.
In 1965 the Minnesota Legislature amended the State Statutes to permit drivers to make a right turn on a red light (RTOR) after stopping, but only where "permissive" signing (Figure I) had been posted. When study and experience failed to reveal evidence which would oppose the use of RTOR, the law was renewed in 1967 and again in 1969. Continued favorable experience led to a change from the "permissive sign" RTOR to a "basic law" RTOR, which became effective on July 1, 1972. On that date, the RTOR became legal except where banned by appropriate signing (Figure II).
During the seven years of permissive sign RTOR, most jurisdictions in the State took advantage of the law (although to varying extents). Initially, signs were placed conservatively and no major problems developed. Gradually, the use expanded until the signs became quite common. Since July 1, 1972 the statewide practice has been to ban the movement only where geometries are unfavorable, where sight distance is limited, or where unusual pedestrian situations exist. The City of Minneapolis is the only jurisdiction with a substantial number of signs posted.
Since no warrants for RTOR had been formally accepted and discussion on the movement continued, a study was conducted to compare driver performance and delay under the pre July 1 permissive signing and the post July 1 basic law. Subsequently, 54 intersections were selected for delay and compliance studies.
The scholastic grading system of letter grades A, B, C, D, and F was proposed as a surrogate scale of freeway traffic quality meeting two conditions. First, most work trip commuters have experienced the school grade system either in grade school, high school or post high school classroom situations, therefore they know that A stands for exceptional performance, B is very good, better than C but not as good as A, C is average, D is less than satisfactory and F is unacceptable or failing. Therefore, it is hypothesized that most commuters understand the grade concept and as a result can interpret in their mind experienced traffic conditions relative to this scale of quality. Second, the grade is a surrogate message that implies certain conditions exist. Since it is only one character long, it can be communicated quickly either by an aural or a visual means.
This paper documents the results of a survey of drivers seeing signs displaying traffic grades at freeway entrance ramps in down.
town Minneapolis, Minnesota. The survey results show that most drivers understand the concept, use the information in route
choice and/or route use considerations and like the concept. These findings lead the author to conclude that the traffic grade concept is valid and should be fully explored.
This study utilized auto occupancy parameter data from three sources: the evaluation of the I-35W Urban Corridor Demonstration Project, the TH 65/Grant Street Carpool Preference Demonstration, and original data gathered quarterly since September 1973 at eight locations around the Minneapolis and St. Paul, Minnesota downtown areas. The purpose of the study was to determine if seasonal, daily or other variations in occupancy parameters were meaningful and to determine if occupancy rates were increasing noticeably due to carpool promotion efforts.
Results of the study indicate that: 1) seasonal differences are not highly significant, statistically, but their existence should be assumed in the design of transportation studies. 2) Daily variations are significant, but not at all sites. Therefore, the existence of daily variation must be assumed when making comparisons so that actual values are not masked. 3) Occupancy rates vary within transportation corridors. Analysis of these variations should be exploited as an evaluation tool. In system planning, existence of these variations must be recognized. 4) The "energy crunch" resulted in a short termed increase in occupancy rates, but these rates have now dropped to pre-crunch levels.
The Capitol Approach Interchange in St. Paul was opened in November 1969, providing a through route for southbound I-35E traffic into the downtown area and to the east and west on I-94. Beginning in the summer of 1968, traffic volumes on I-35E southbound during the morning peak hour were such that congestion and delays occurred between TH 36 and I-94. Breakdowns were almost a daily certainty, with the Maryland Avenue Ramp area the most severely affected.
Several factors were suspected as possible causes, including:
1. inadequate downtown ramp terminal capacity.
2. roadway geometries, generally.
3. restricted width of the Cayuga Bridge, specifically.
4. weaving traffic.
5. combination of several of the factors.
In January of 1969 the Traffic Research Section sought to determine the actual cause of the congestion and to recommend relief measures This activity culminated in the I-35E Ramp Metering Study conducted in July 19&9. This report covers the first in a series of Ramp Metering studies to be conducted in the Twin City Metropolitan Area by the Minnesota Highway Department
As has been the situation in other major metropolitan areas, the recurring peak hour congestion problem has illustrated a need for freeway operation beyond the signing, striping, police and maintenance activity. It is now also apparent that surveillance and control measures are but a part of a necessary Traffic Management System incorporating the full range of detection, observation and response capabilities.
This report documents the activities of the Minnesota Highway Department in the area of freeway surveillance and control and how these activities are in keeping with an ultimate Traffic Management System for the seven county Twin Cities Metropolitan Area. Current projects are located on I-35E in St. Paul/Ramsey County and I-35W & 1-94 in the Minneapolis/Hennepin County area (Figure 1).
This report, the third on ramp metering experience on I-35E in St. Paul, Maplewood and Little Canada, presents results of an evaluation of the traffic responsive system installed in 1971. The system was approved by the Federal Highway Administration as a Category II - Experimental" project. This report is intended to fulfill the requirements of the Category II approval.
This report presents an overview of the freeway surveillance and control system provided for the I-35W Corridor as part of the Urban Corridor Demonstration Program. This program is a U.S. Department of Transportation effort involving the Federal Highway Administration and the Mass Transportation Administration. The objective of this program is to find ways and means to reduce peak period congestion in urban area transportation corridors.
The I-35W Urban Corridor Demonstration Project was a test of the "Bus-On-Metered Freeway" concept. Access to I-35W was controlled by a computer coordinated traffic management system to provide a high level of service for the line-haul portion of the express bus trip on the freeway. Nine special bypass ramps provided preferential treatment for the express buses. The use of these same ramps for carpools was considered early in the planning stages of the project. It was decided not to proceed because of possible interference with the project evaluation.
Following completion of many of the project tasks, this study was begun to assess the desirability and feasibility of providing preferential treatment as a means to promote formation of carpools. Factors considered included potential impact on the level of congestion, actual delay savings, potential delay savings, operational problems, costs, definition of a carpool and enforcement problems. Each metered ramp in the system was analyzed individually to determine if preferential treatment was feasible.
The study concluded that preferential treatment was indeed feasible at six locations. A carpool definition of three or more occupants per vehicle is preferred. Implementation of preferential treatment at the Grant Street ramp is recommended, with a careful evaluation to be completed before the other five locations are initiated.
