Frequently asked questions

While there are many factors that may have a potential to influence traffic noise, traffic volume is the predominant factor. With that said, traffic is at its loudest when the traffic operates at Level of Service C. This is the condition of a stable flow of vehicles, at or near free flow in a lane, but lane changing and maneuverability may be challenging. During Level of Service C at 70 mph, there are approximately 1,500 vehicles per hour and per lane. When traffic volumes increase beyond Level of Service C, vehicle speeds decrease and lower the noise levels.

ADOT utilizes data collected from the permanent automatic traffic recorders, an integral part of ADOT’s traffic data management system. That data will provide hourly/daily traffic patterns which, in turn, will provide the periods that the freeway operates at or close to “level of service c” – the highest level of traffic noise based on traffic volume and travel speeds. ADOT will continue to evaluate data and determine 2.5-hour windows of time - in the morning and afternoon - with similar traffic volumes when testing would occur.

Measurements will be taken at representative locations along the South Mountain Freeway; that is, residential neighborhoods, parks, schools and similar locations. Measurements are typically restricted to exterior areas of frequent human use. Interior measurements are taken only when there are no outside activities, such as at churches, hospitals and libraries.

Because of the COVID-19 pandemic, average daily traffic volumes throughout Maricopa county are lower than usual. Taking noise measurements during this pandemic is not representative of typical traffic noise levels. ADOT is planning to resume field noise testing in late summer/early fall 2020 and in late February/early March 2021. Beyond that, ADOT will continue testing noise levels throughout the 22-mile corridor regularly in select locations. Schedules are subject to change because of the pandemic and other unforeseen situations.

“Fully operational” means that the monitoring systems and overall conditions on the freeway are conducive to continuous, uninterrupted, and free-flow traffic operations, and that the traffic volumes are aligned with the levels predicted by the Maricopa Association of Governments (MAG) travel demand model for the year 2020.

ADOT is conducting noise measurements in compliance with the Final Environmental Impact Statement (FEIS) for the South Mountain Freeway. Further, ADOT will evaluate the common noise environment within the project area after the freeway is “fully operational.”

The price tag of modern roundabouts versus traditional traffic-control methods can vary. Demographics, geography and environmental elements all make a difference when engineers, communities, and city and state planners begin to consider how to move traffic from one street to another.

While it depends on the number of pedestrians and vehicles, in many instances, a modern roundabout can be safer for pedestrians than a traffic signal. Pedestrian crossing is reduced to two simple crossings of one-way traffic that is proceeding at relatively slow speeds. Pedestrian safety is improved further by the a pedestrian crosswalk sign placed right where a vehicle enters a modern roundabout. Even with this precaution, it is recommended that pedestrians always use caution and designated crosswalks.

In most situations, a modern roundabout can handle higher traffic volumes with less delay than traffic signals because motorists do not stop for traffic lights. A two-lane roundabout will handle the same capacity as other major intersections in the Valley, and a three-lane roundabout handles up to 6,000 vehicles per hour.

First, slow down! You should approach a modern roundabout at no more than 25 mph. Most importantly, do not merge. Always yield to traffic in circulation when entering a modern roundabout. Do not attempt to cut in front of traffic, but wait for a safe gap. The drivers already in the roundabout have the right of way.

No, a modern roundabout is not a four-way stop. Both intersections are what the engineering community calls a “method of moving traffic,” but four-way stops require all traffic to stop prior to entering the intersection. Modern roundabouts require motorists to yield at entryways. All traffic entering a modern roundabout must follow the golden rule of the modern roundabout: Never merge. Here are some other differences between roundabouts and four-way stops.

Many traffic circles require circulating vehicles to grant the right of way to entering vehicles and can be very large or very small. They can operate at higher speeds and often require motorists to move from one lane to another.

Modern roundabouts include improvements such as yielding to as opposed to merging with circulating traffic, deflection at entry and low-speed entry by design.

The Arizona Department of Transportation manages implementation of the Arizona STSP and is a primary stakeholder as are the Arizona Department of Public Safety, Arizona Department of Health Services, Governor’s Officer of Highway Safety, Federal Highway Administration, National Highway Traffic Safety Administration and Federal Motor Carrier Safety Association. Hundreds of other stakeholders, representing municipalities, law enforcement, emergency responders, hospitals and health services providers, safety organizations, and more serve on Emphasis Area teams.

Every year, preventable crashes result in hundreds of fatalities and thousands of serious injuries on Arizona roadways. The purpose of the STSP is to direct transportation-project investment decisions and assure best practices are adopted to achieve a significant reduction in transportation related fatalities and serious injuries on all public roadways.

Based on the most recent analysis of statewide crash data, Arizona has identified five emphasis areas. These emphasis areas are a required component of any STSP and help direct resources, focus implementation efforts, and organize emphasis area teams. The five emphasis areas are: Highway Safety (Behavior-Related), Intersections, Lane Departure, Pedestrians and Safety-Related Data.

A Strategic Traffic Safety Plan (STSP) is a statewide, coordinated plan that provides a comprehensive framework for reducing fatalities and serious injuries on all public roads. The STSP is developed by the Arizona Department of Transportation in cooperation with local, regional, state, federal, tribal, non-profit and private-sector safety stakeholders. The STSP is a data-driven, multiyear plan that establishes statewide goals and objectives and identifies Emphasis Areas that must be addressed to reduce traffic fatalities and serious injuries.