Yield roadways: An Introduction

A low cost strategy for rural regions to begin building a network for everyone to share.

What are they?

Small rural roads like those surrounding Kennett can be charming, and so it is no surprise to find residents walking or biking on many of them. But these also present a different set of challenges, like narrow roads, drivers who speed, sections with limited sight distance, and so on.

A Yield Roadway is one of several Mixed Traffic designs. Pedestrians, bicyclists, and two way motor vehicle traffic share the same, slow-speed travel area without center line markings.

The FHWA recognizes this design as a potentially appropriate option for minor rural roads with low volumes (Average Daily Traffic or ADT less than 2000/day) and low speeds (e.g., less than 30mph).

How do they work?

Drivers stay in the middle of the road, but can shift towards

  • The edge on their right to allow another car to pass, but they must yield to any cyclists or pedestrians
  • The edge on their left to give extra room to a cyclist or pedestrian traveling in the same direction
  • Cyclists can shift towards the center to pass pedestrians when cars are absent

Drivers do many of these things already - they yield to other drivers every day, all over Kennett

  • They refrain from passing cyclists on a narrow road when another car is coming
  • They yield when approaching a one-lane bridge (like on Hillendale next to Chandler Mill)
  • They yield when a delivery truck blocks their lane.
  • And the current design for the Chandler Mill Trail includes two one-way yield sections.

Some designers have recommended additional markings (an appropriate option according to AASHTO). For example, adding two dashed lies 5’ from the each edge pf the roadway to suggest a 10’ wide center travel area for cars on a 20' wide roadway can help make this design even safer and more comfortable for cyclists, pedestrians, and drivers.

This is like an Edge Lane Road (ELR) except that the edge of the road is not a lane designated for cyclists, but an area suggested for cyclists and pedestrians.

  • As a Yield Roadway, designers use 2x Head On Stopping distance (HOSD) to identify sections with limited sight distance, instead of the much more conservative passing sight distance (PSD) used with ELRs.
  • And there is no requirement to submit a Request to Experiment to implement a Yield Roadway.

What are some of the challenges of this design?

Speed is perhaps the most common challenge to implementing a Yield Roadway in a rural region, where people tend to drive fast. Even on small roads, at least some drivers are likely to exceed 30mph. 

  • Start with a traffic study: is speed an issue? 

Another significant challenge are sections with limited sight distance (aka a blind curve or hill). These occur when a driver cannot see far enough ahead to safely come to a stop if an oncoming car is pulling around a cyclist or pedestrian.

  • These can be created by roads with hills, or curves (like this section of Burnt Mill Road to the left), especially when bushes or embankments block the view.

Whether or not a section of roadway has limited sight distance can really depend on the speed of cars (see  left )- for example, two cars traveling 30mph need 305 feet to safely stop (the Head On Stopping Distance or HOSD), while those traveling at 20mph need only 165 feet to safely stop.

This also suggests some solutions:

  • Bushes/embankments can be shaved to improve visibility (see right), or; 
  • Other traffic calming measures can be added immediately before the section to drop speed such that cars now have enough room to stop safely, based on the revised HOSD. For example, speed bumps can reduce speeds by 6-8mph

If neither is successful, the section can be bypassed with a short 10’ wide off-road shared-use section.

Though sight distance is not formally included in ratings of the Level of Traffic Stress (see below), it is clear that this impacts the stress experienced by cyclists.

Concerns about speed in relation to limited sight distance should also be re-evaluated on extremely low volume roads (e.g., less than 400 vehicles/day). Traffic counts provided by the Delaware Valley Regional Planning Commission (DVRPC) suggest that many smaller roads in Kennett may reach this threshold.

Research demonstrates that decreasing traffic volume becomes more important than speed in determining the safety and comfort of low-volume, mixed traffic facilities, with the risk decreasing exponentially as a function of decreasing in traffic volume - for example decreasing almost 90% when volume drops from 1600 to 400/day. 

  • Consider recalculating the risk for a given section of road. It is possible, for example, that the risk of two speeding cars encountering a cyclist on a specific section of road may only occur once every 5-10 years on an extremely low volume road.

If a Yield Roadway is intended for use by pedestrians, designers must also ensure that it meets accessibility guidelines (see  PROWAG ).

  • It is possible that sections might not meet full accessibility guidelines (for example, where there are hills with excessive grades, or excessive cross-slopes because of the crown of the road or where curves have been super-elevated).
  • If these features cannot be corrected, it is possible that the design might only meet the needs of cyclists.

What are some of the many advantages of this design?

The FHWA identifies many potential benefits of yield roadways (see left).  We would also note that, compared to a traditional shared use path running alongside the road, it 

  • Is a fraction of the cost;
  • Has no environment impact, and;
  • Precludes the need to seize private land.

Eliminating center line markings is a key feature of a Yield Roadway that encourages drivers to travel in the center of the road when no one else is present. According to the FHWA, this introduces “helpful traffic friction and ambiguity, contributing to a slow speed operating environment”. But practices vary from state to state.

A  recent review  of similar designs suggests that driving closer to the center may help to reduce accidents by 44%. Why? Drivers who stay predominantly in the center lane are less likely to crash either by simply drifting off of the edge of a narrow road or by then overcorrecting. 

  • Another advantage? Vehicles traveling in the center of the road reduce wear on the vulnerable edge of the roadway!

A Yield Roadway can be comfortably shared with most cyclists according to the Bicycle Level of Traffic Stress (LTS) framework in the most  recent ratings 

  • It is comfortable for children as young as 8 (LTS 1) even on a street with 1500 vehicles/ day and prevailing speeds of 28.5mph.
  • Removing the centerline matters - for example, it helps to keep a road with 1000-1500 vehicles/day comfortable for all cyclists under 28.5 mph.  
  • The LTS model was developed for urban areas, however. Its authors explicitly acknowledge that it does not take into account sight distance and steep uphill grades, factors that would increase the LTS rating. 

As noted earlier, yield roadways can also help to calm traffic - e.g., to help drivers slow down and to be more vigilant. This may sometimes be more comfortable for drivers than other strategies like speed bumps when calming a longer stretch of roadway, and less noisy than rumble strips for neighbors.