Agenda - Council - 07/27/1999 - Laserfiche WebLink

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July 1, 1994 9-4.00 (Continued) TRAFFIC ENGINEERING MANUAL -- rI Studies which will be helpful in assessing and demonstrating the need for a signal are the following: Volume studies, including approach volumes, turning movements, and peak hour detail counts; Pedestrian counts, including any unusual numbers of children, handicapped, and elderly; Traffic gap studies; Speed studies; Accident studies; Intersection delay studies. Procedures for doing various traffic studies are found in the Institute of Traffic Engineers' Manual of Traffic Engineering Studies and in Chapter 6 of the Traffic Engineering Manual. The studies which are required to be included in a signal justification report are discussed below, and in section 4C-1 of the MN MUTCD. 9-5.03.01 Traffic Signal Warrants Warrants have been developed to determine if an intersection needs some type of intersection control. Justification for a signalized intersection should be based meeting one or more of the established warrants as stated in the Minnesota .Manual on Uniform Traffic Control devices. Traffic signals should not be installed unless one or more of the signal warrants in the MN MUTCD are meet, but the 'meeting of a warrant or warrants does not alone justify the installation of a signal. The data that was collected as part of the engineering studies should be used in combination with the warrants to justify.the need to install the traffic control device. The engineering study should show that the intersection will benefit in improved safety and/or operation. The traffic signal warrants are stated in section 4-C of the Minnesota Manual on Uniform Traffic Control Devices. The statements that follow gives intents and interpretations of the warrants. WARRANTS 1 AND 2: Warrants 1 and 2 are the warrants that pertain to volumes, and are the most common warrants for justifying intersection control. The same eight hour period must be used for both the Major and the Minor Streets. Mn/DOT policy on the use of the speed reduction factor is that ifa mainline has a posted speed limit of 70 km/h (45 mph) or above, that is sufficient evidence that the 85th percentile speed is above 60 km/h (40 mph), and a speed study is not required. The population reduction factor mentioned in Warrants 1 and 2 states that an intersection lying "within the built-up area of an isolated community having a population of less than 10,000...". In the seven-county metropolitan area, it is often a judgment call whether a community is isolated or not. There are no strict criteria on this. Geometrics play an important part in determining the volume requirements for Warrants 1 and 2. WARRANT 3: This warrant allows the installation of a traffic signal if there is a considerable number of pedestrians. To meet warrant 3 there must be pedestrian volumes of at least 100 pedestrians for any of four hours, or a peak hour volume of 190 pedestrians. These volumes can be reduced by 50 percent if the crossing speed of the pedestrians is predominantly below 1.1 meter per second (3.5 feet/sec). A gap study must be completed to determine that there are less than 60 gaps of adequate length in an hour. If a signal is warranted, the signal should be traffic actuated with pedestrian indications. WARRANT 4: The Institute of Traffic Engineers' Program for School Crossing Protection contains the method Mn/DOT recommends for addressing Warrant 4. Warrant 5: A signal justification report addressing Warrant 5 should contain a time-space diagram of the proposed intersection and nearby signals, helping to demonstrate that a progressive system will help maintain platooning and group speed. Signals are installed under Warrant 5 on the basis of the 85th percentile speed, so a speed study is necessary for this warrant. It is expected that any signal installed under Warrant 5 would include interconnect. Warrant 6: The 80% requirement is not the same as the 80% required for Warrant 8. For Warrant 6, the requirement is 80% of Warrant 1, Warrant 2, or Warrant 3. Signal justification reports which'address Warrant 6 are to include an accident diagram. A time-space diagram showing the proposed signal system will not seriously disrupt progressive traffic flow should be included. Discussion of the failure of less restrictive remedies is also required by the MN MUTCD. Current~n/DOT policy is that in general, Warrant 6 is not applicable to an intersection which is already signalized. I I I 9-13