A Flex Route is an active traffic management system that promotes safety and helps manage rush hour and seasonal traffic congestion by utilizing the median shoulder as a temporary fourth lane.

Ramp meters are traffic signals installed on freeway on-ramps to control the frequency at which vehicles enter the flow of traffic on the freeway. Ramp metering reduces overall freeway congestion by managing the amount of traffic entering the freeway and by breaking up platoons that make it difficult to merge onto the freeway.

MDOT installed Michigan’s first Flex Route system on US-23 north of Ann Arbor, from M-14 to M-36 in November 2017. I-96 Flex Route will be Michigan’s second installation of Flex Route technology.

I-96 between Brighton and Novi was selected for a Flex Route because it is an area where rush hour traffic congestion is commonplace, the surface needed to be rehabilitated, and the geography and narrow confines of the MDOT right of way made other options prohibitively expensive. The three-hour pulses of heavy traffic during morning (eastbound) and evening (westbound) rush hours, and relatively lighter traffic outside of these time blocks, allowed us to right-size the solution to the problem using traffic management technology.

The I-96 Flex Route construction project started in Spring 2022 and is scheduled to be completed Fall 2024. 

The Flex Route temporary lanes will be opened for travel as needed during peak travel periods – typically during the morning commute on eastbound lanes and the evening commute on westbound lanes – and when traffic is backed up because of temporary conditions, such as bad weather, traffic incidents or construction.

The Flex Route will be monitored by MDOT’s Southeast Michigan Transportation Operations Center (SEMTOC). The SEMTOC is a seven-day-a-week operation center that houses dispatchers from MDOT and Michigan State Police. The agencies share resources and information by monitoring traffic sensors, distress calls, and video feeds from cameras. They also coordinate their efforts with law enforcement agencies and other transportation officials.

Flex Route will be connected to the Southeast Michigan Transportation Operations Center (SEMTOC) by intelligent transportation systems (ITS) technology. This will include an intelligent lane control system consisting of overhead signs, cameras, and electronic message boards, which SEMTOC employees will monitor and adjust as needed.

If a traffic condition develops, the SEMTOC will adjust the Flex Route through electronic lane control signs mounted above each lane. These signs will show motorists which lanes are available and provide the recommended speed for the current travel conditions. SEMTOC operators will also monitor and adjust the ramp metering as needed.

Any traffic incidents will be managed by the State Police with assistance from MDOT’s Freeway Courtesy Patrol (FCP) and several new crash investigation sites that will be strategically located along the corridor (east and west bound).

When you enter the ramp, you will see a yellow sign that reads, “Ramp Metered When Flashing”. If this sign is not flashing, then you can continue driving as usual, as you would on any other ramp. However, if the sign is flashing, then you will know to prepare to stop ahead at the traffic signal and stop bar or the vehicle in front of you.

As you approach the traffic signal, form two lanes, and come to a complete stop at the red signal as you would for any other traffic signal. Each lane has its own signal. The left signal controls the left lane, and the right signal controls the right lane. The signals alternate between the two lanes, allowing one car to enter the freeway at a time. When the traffic signal next to you turns green, you can proceed to enter the freeway.

A large green arrow posted above the median shoulder (flex lane) will show when that Flex Lane is available as a fourth lane.

A large red X above the median shoulder (flex lane) will show when the Flex Lane is not to be used.

For more details, view the Flex Route 23 brochure and video.

Trained operators in MDOT’s SEMTOC will use traffic sensors and real-time camera images to monitor travel conditions. This data will enable them to identify any slowdowns, traffic incidents and/or lane blockages ahead.

SEMTOC operators will plan to open the shoulder (flex lane) for peak traffic periods, eastbound in the morning and westbound in the afternoon. SEMTOC will also respond in real time to current travel conditions. For example, when traffic slows to speeds pre-established in guidelines, operators will open the flex lane and start ramp metering accordingly. They also will post appropriate safety information to guide motorists, such as lane blockages ahead and recommended speeds for existing conditions.

Ramp metering smooths the flow of traffic onto the freeway which helps to accomplish two things:

1. Reduce congestion by managing the number of vehicles entering the freeway at one time.

2. Improve safety by breaking up large groups of vehicles that form on the ramp and have difficulty entering the freeway.

A 24-hour fix simply is not necessary on corridors that typically experience traffic slowdowns only during regular peak travel periods. It is more cost-effective to adapt the shoulder for use as a temporary fourth lane than it would be to install a full time fourth lane. Employing Flex Route technology maximizes capacity of existing infrastructure for less money.

Implementing a Flex Route requires less capital investment than adding another lane – primarily because it works within the existing infrastructure and doesn’t require the same degree of expansion to implement.

A lower recommended speed would be posted, for example, if motorists were approaching a traffic incident or other circumstances where slower speeds would promote safer travel, such as inclement weather and slippery roads

The ramp metering system will adapt to real-time traffic conditions. Vehicle detectors along the I-96 freeway and ramps will determine how fast the traffic signal will cycle from red to green, and the metering rate will adjust as needed to maximize the flow of traffic throughout the corridor.

When sensors along the ramps detect lengthy traffic queues, the metering rate will speed up so to help minimize wait time on the ramp, and to prevent traffic queues from spilling into local roadways.

Vehicle detectors will be placed at multiple locations along the freeway entrance ramps to detect the length of traffic queues. As the line of cars grows, the metering rate will speed up to allow more cars to enter the freeway. A vehicle detector placed near the end of the ramp, where it meets the local roadway, will detect when traffic queues are about to reach the local road, and will prompt the system to increase the metering rate to the fastest possible rate to clear vehicles from the ramp.

MDOT is planning a robust driver education campaign prior to the Flex Route opening to familiarize motorists with how to drive a flex lane and ramp metering. Drivers need to familiarize themselves as to how a Flex Route works; they can start by viewing the US-23 Flex Route video. If a driver is uncomfortable driving the Flex Route, MDOT recommends they handle it the same way that drivers should handle most any traffic situation: slow down and stay to the right.

I-96 Flex Route will provide the communications backbone and technology to support connected autonomous vehicles (CAV) and vehicle-to-infrastructure (V2I) technology.