17.2.4. Creeper lane

When the uphill climb is extremely long, it may be desirable to introduce an additional lane so as to allow slow ascending vehicles to be removed from the main stream so that the fast moving vehicles are not affected. Such a newly introduced lane is called creeper lane.

A creeper lane is an extra lane added to a steep uphill section of road. Its main purpose is to allow slower vehicles, like trucks or heavily loaded cars, to move out of the way, letting faster vehicles pass unobstructed. This is especially important on long climbs where slow vehicles can significantly hinder the flow of traffic.

Think of a creeper lane like a slow-moving escalator in a busy station. If people who are just standing still don't move aside, those who wish to walk faster find themselves stuck. By creating a separate lane for slower traffic, faster vehicles can glide past without getting stuck, ensuring smoother travel for everyone.

There are no hard and fast rules as when to introduce a creeper lane. But generally, it can be said that it is desirable to provide a creeper lane when the speed of the vehicle gets reduced to half the design speed.

While there isn't a strict rule for when to add a creeper lane, a common guideline is to do so when vehicles begin traveling at half of the expected speed. This slow speed often indicates that the uphill slope is becoming challenging for many drivers, and introducing an extra lane can help manage the situation effectively.

Imagine riding a bike up a steep hill. If you notice that everyone else around you is barely moving and struggling, it would be helpful if there was a separate path for those who can handle the incline better, allowing you to keep pedaling at your own pace without getting bogged down by slower riders.

When there is no restrictive sight distance to reduce the speed of the approaching vehicle, the additional lane may be initiated at some distance uphill from the beginning of the slope. But when the restrictions are responsible for the lowering of speeds, obviously the lane should be initiated at a point closer to the bottom of the hill.

The decision on where to start a creeper lane largely depends on visibility and traffic conditions. If drivers can see clearly ahead and there's no reason to slow down significantly, the creeper lane can begin farther up the slope. Conversely, if sight distance is limited or there's a reason drivers need to slow down earlier, the creeper lane should start closer to the bottom of the hill to effectively accommodate slower vehicles.

It's like setting up a slow lane on a highway. If drivers can see the uphill stretch well, they can be directed to the slow lane further along. However, if their view is blocked by curves or intersections, it's better to guide them to that slow lane sooner, so they aren’t caught off guard and can transition smoothly.

Also the creeper lane should end at a point well beyond the hillcrest, so that the slow-moving vehicles can return back to the normal lane without any danger. In addition, the creeper lane should not end suddenly, but only in a tapered manner for efficient as well as safer transition of vehicles to the normal lane.

It's important for the creeper lane to finish safely, ideally after the top of the hill, allowing vehicles that have been traveling slowly to merge back into the normal traffic flow without rushing. A gradual tapering off of the creeper lane helps ensure that vehicles can merge smoothly, minimizing the risk of accidents as they rejoin faster-moving traffic.

Consider merging lanes on a freeway. A lane that ends abruptly can cause confusion and accidents. But if the lane gently tapers off, it's much easier for drivers to blend into the main flow of traffic without sudden stops or lane changes that can lead to collisions.

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