US-23 to Become Michigan's First "Flex Route"

[Scottathew]

A portion of US-23 between Ann Arbor and Brighton will become Michigan's first "Flex Route".

A Flex Route does the following:
- Allows traffic to use an upgraded shoulder for travel during peak times
- Uses electronic signage to dynamically open and close lanes
- Uses electronic signage to suggest speeds based on real-time data
- Adds a lane to congested areas with very little additional cost by utilizing the shoulder during rush hour

[1953]

So, why not just leave the lanes open all the time?

And, speed limits are LIMITs, so, why would I need to regulate them? Don't they kind of self-regulate?

What nonsense is this?

1953

[Wesley Mouch]

So, why not just leave the lanes open all the time?

And, speed limits are LIMITs, so, why would I need to regulate them? Don't they kind of self-regulate?

What nonsense is this?

1953

As to shoulder use, a possible reason for only allowing during peak use is that you might only pay for a 'hot' tow-truck during peak use. So between 7-9 and 4-6 there would be a tow ready to remove any dead vehicle quickly -- where the rest of the time you'd rely on drivers just pulling over and waiting for the tow driver to wake up, shave, and finish their morning coffee.

Efficient use of assets is of value.

As to speed limits, I don't know why it matters. Perhaps a slower speed limit reduces the stop & go effect on freeways and increases throughput? [[Have you seen that video of cars in a circle and how they naturally head towards stop & go?

[Scottathew]

So, why not just leave the lanes open all the time?

And, speed limits are LIMITs, so, why would I need to regulate them? Don't they kind of self-regulate?

What nonsense is this?

1953

One reason I can think of is because the third lane is less safe, as there is no shoulder. That way they can have the safety of a shoulder when capacity isn't needed. When there are less cars, speeds are faster, and thus the safety of a shoulder is needed.

[Sandhouse]

Wesley is very close to the explanation of adjustable speed signs. The idea is indeed to try to smooth traffic flow so that it doesn't deteriorate to stop-and-go travel, as in the circle-of-cars demonstration.

Variable speed limits are in use in Europe, especially in Britain, where they say they get good results from them in terms of safety and delay. The limits are enforceable there. Experiments in this country have not yielded similar results. Variable limits are only suggestions here. My theory is that Americans are so used to meaningless, too-low limits that they habitually ignore the signs and go at normal speeds until someone slams on their brakes and slows everything down.

Advisory limits on I-70 west of Denver are said to be improving traffic flow to the ski-resort territory, where it is not possible to widen the freeway. The US-23 experiment will be an interesting test of self-regulating systems.

[Jimaz]

Here's a video that explains phantom traffic jams & variable speed limits:

Traffic Waves

[Hamtragedy]

They've been using the shoulder as rush-hour drive lanes in the Boston Area for decades.

Kinda reminds me of the left-turn lane control we used on streets like Woodward, Grand River, Jefferson, Gratiot, Warren, etc up until the mid 90s, where making a left turn during rush-hours was illegal, and inbound and outbound traffic used that lane.