Traffic Safety and Traffic Control Frequently Asked Questions

Stop Sign FAQ's

What is the primary reason for stop signs?

Stop signs are installed at intersection where drivers cannot safely apply the right-of-way rule and an increase in motor vehicle accidents results.

What is the right-of-way rule?

The right-of-way rule states that: when a motorist approaches an uncontrolled intersection (an intersection without any traffic safety control device) they must yield to any driver on their right who approaches the intersection, regardless of which vehicle reaches the intersection first. (Reference: ORS 811.275)

Why not use stop signs to control speeding?

The City receives regular requests from residents to install stop signs as a speed control measure.  Several studies have shown that using stop signs to control speeding does not bring about the desired results.  When stop signs are used to slow speeding, drivers tend to increase their speed between signs or intersections to compensate for the lost time due to stopping at stop sign.  Studies also indicate that some drivers will accelerate rapidly after a stop, which exacerbates an already unsafe condition.

What happens when stop signs are improperly placed?

Too many stop signs can cause motorists to ignore the right-of-way rule or just plain ignore the stop sign itself.  Erecting stop signs in a neighborhood can also result in increased levels of pollution and noise.  Placing stop signs in one location can cause adverse impacts on nearby streets since many drivers will seek new routes to avoid the stop signs.  This can lead to new traffic problems and complaints in adjacent neighborhoods.

Who decides whether a stop sign is needed?

The City determines where to place stop signs so that they provide the best benefit to the neighborhood and City as a whole.  The City's Engineering Division, working alongside Public Works Operation and Police make the final determination on the placement of stop signs after considering the following: traffic flow, volume, intersection configuration, and traffic accident reports.

What is the criteria for placing a two-way stop sign?

The City can consider placing a two-way stop sign at an intersection if the following criteria are met:

• Where a street enters a through street; where a safe approach speed is less than 10 mph due to a permanent visibility obstruction such as buildings, trees or shrubs.
• Where accident history indicates three or more reported crashes over the last three years, and the crashes could have been avoided by the use of a stop sign.
• Where circumstances and crash history indicate that observing the normal right-of-way rule could still be hazardous, resulting in traffic accidents.

What is the criteria for placing four-way or all-way stop signs?

In most cases, a two-way stop sign is sufficient to define who has the right-of-way. A four-way or all-way stop is considered an option only when an intersection with an existing two-way stop is the site of numerous crashes or is experiencing a significant traffic congestion problem.  The criteria for four-way al all-way stops are:

• On local streets where there has been five or more reported crashes within a two-year time period.
• On through streets where within a two-year period the intersection had 1.5 crashes or more per million vehicles entering the intersection and the accidents would likely have been prevented by a four-way stop.
• Where the number of vehicles entering an intersection averages at least 500 vehicles per hour for any eight hours of a typical day and the combined vehicular and pedestrian volumes from the minor street averages at least 200 per hour for the same eight hour period.

Speeding FAQ's

What are rational Speed Limits?

Rational Speed Limits promote public safety by helping drivers choose a reasonable and prudent speed that is appropriate for normal traffic, weather and roadway conditions. They encourage more drivers to travel at about the same speed, which has been shown to reduce the likelihood of crashes. Rational Speed Limits make more sense to the vast majority of drivers because they are neither unrealistically low nor high, thus they are largely self-enforcing.

How are they created?

A team of traffic engineers and public safety officials analyzed traffic flow and speed data from many locations along the roadway. They also reviewed historical crash data and considered the existing roadway design characteristics. This information was combined to select a reasonable and prudent speed limit that is consistent with the speeds chosen by the vast majority of drivers. The starting point for determining the new speed limit is the 85th Percentile Speed.

What is the 85th Percentile Speed?

Most drivers behave in a safe and reasonable manner, do not drive at excessive speeds and do not want to get in crashes. The 85th Percentile Speed is usually slightly slower than the upper bound of speed that includes these generally prudent drivers.  Research has shown that vehicles traveling between the 50th and 90th percentile of speed have the lowest risk of crashing due to speed. Drivers who exceed the 90th percentile have a significantly higher risk of crashing. Laws are intended to protect the public by regulating unreasonable or unsafe actions. The 85th Percentile Speed is a reasonable basis for the speed limit.

Will a rational speed limit be more difficult to enforce?

It should be less difficult to enforce than the current speed limit and is usually met with less driver objection, thus maintaining respect for law enforcement. It is a speed limit that seems fairer to drivers because the vast majority already drive at or below that speed without crashing. With rational speed limits, 85-90 percent of drivers are within the law.

Miscellaneous Signs FAQ's

The City receives multiple requests for a variety of miscellaneous signs throughout each year.  Some of the most common requests (beyond stop signs) are:

No Parking - Children at Play - Cross Traffic Does Not Stop - Pedestrians in the Roadway

The City adheres to all State and Federal regulations with regards to the installation of road signs.  The City also abides by the Manual on Uniform Traffic Control Devices (MUTCD).

Excessive use of signs:  (MUTCD 2A.04) - Regulatory and warning signs should be used conservatively because these signs, if used to excess, tend to lose their effectiveness. If used, route signs and directional guide signs should be used frequently because their use promotes efficient operations by keeping road users informed of their location.

Classification of Signs Standard:  (MUTCD 2A.05) - Signs shall be defined by their function as follows:

A. Regulatory signs give notice of traffic laws or regulations.

B. Warning signs give notice of a situation that might not be readily apparent.

C. Guide signs show route designations, destinations, directions, distances, services, points of interest, and other geographical, recreational, or cultural information.

Crosswalk and Flashing Beacon Crossing FAQ's

Where are crosswalks installations recommended?

Crosswalks are generally marked at intersections where there is substantial conflict between vehicle and pedestrian movements, where significant pedestrian concentration occurs, where pedestrians could not otherwise recognize the proper place to cross, and where traffic movements are controlled.  Examples include:

• Approved school crossings
• Signalized and four-way intersections
• All-way stop controlled intersections where there is significant pedestrian traffic and one or more crossing locations have been prohibited.

Why aren't crosswalks recommended in the middle of a block?

Research studies suggest that marked crosswalks give pedestrians a false sense of security and decreases their safety awareness. Pedestrians often step off the curb into a crosswalk assuming that the approaching vehicle will stop. Although drivers must yield the right-of-way to pedestrians at crosswalks, it is the pedestrians responsibility to be cautious and alert before entering the crosswalk.

At mid-block crosswalks, traffic is not controlled by stop signs or traffic signals.  Additionally, mid-block crossing frequently have reduced visibility due to elevation or curves within the road.  These marked crossings may not always be readily apparent to drivers from a safe stopping distance.

Information on the use of Flashing Beacons

The Manual on Uniform Traffic Control Devices (MUTCD) gave interim approval to Rectangular Rapid Flash Beacons (RRFB's) for optional use in limited circumstances in July 2008. The interim approval allows for usage as a warning beacon to supplement standard pedestrian crossing warning signs and markings at either a pedestrian or school crossing; where the crosswalk approach is not controlled by a yield sign, stop sign, or traffic-control signal; or at a crosswalk at a roundabout.

RRFBs are user-actuated amber LEDs that supplement warning signs at unsignalized intersections or mid-block crosswalks. RRFBs use an irregular flash pattern that is similar to emergency flashers on police vehicles.They can be activated by pedestrians manually by a push button or passively by a pedestrian detection system.

 - RRFBs may be installed on either two-lane or multi-lane roadways.

 - Cost is approximately $10,000 to $15,000 for purchase and installation of two units (one on either side of a street). This includes solar panels for powering the units, pad lighting, indication units (for both sides of street) with RRFBs in the back and front of each unit, signage on both approaches, all posts, and either passive infrared detection or push buttons with audio instructions.

More information about RRFB's can be found via the U.S. Department of Transportation Federal Highway Administration or by clicking -here. 

Speed Bumps, Humps and Cushions FAQ's

The City of West Linn works in conjunction with emergency response agencies to ensure that roadways within the City are easily and safely accessible for emergency response vehicles including ambulances and fire trucks.  Installation of speed bumps can adversely affect emergency response vehicles by:

• Reducing response times between 1 and 9.2 seconds per bump depending on the size of the bump (study commissioned by TVF&R and completed by DKS Associates).
• Increased wear and tear on vehicles as repeated shocks as well as sudden and heavy impacts affect the suspension, frame, and drive train of emergency response vehicles.
• Detrimental effects to patients during emergency medical response services (EMS) transport.
• Injuries to firefighters as fire apparatus is driven over vertical bumps.

Due to the impact of speed bumps on emergency response times, vehicles, and potential effects on patients and first responders during transport, the Traffic Safety Committee does not currently recommend new installation of speed bumps, humps or cushions on ANY City street.  A map of our City’s street system can be accessed here and provides additional information on street classifications.

Setting Speeds

Speed Zone Standards are in place in the event a speed limit is not posted and are as follows:

15 mph- Alleys, narrow residential streets

20 mph- Business districts, school zones

25 mph- Residential districts, public parks, ocean shores

55 mph- Open and rural highways, trucks on interstate highways

65 mph- Autos on interstate highways

The Basic Rule

The Basic Rule applies as a final word in Oregon for motorists on all public streets and highways. The Basic Rule is a safety valve and acknowledgement that drivers are to act independenttly, reasonably and with good judgement. This rule states that motorists should drive a speed that is reasonable to sorrounding traffic, weather and road conditions.

What happens when a speed zone change is requested and who authorizes changes?

When a speed zone change is requested the Oregon Department of Transportation is responsible to investigate and issue a decision. An engineering study will be started and the road will be survery for a number of different factors to make a decision. When determining if the speed zone change is warrented the 85th percentile is typically used.  That recognizes that the speed at or below which 85 percent of drivers travel is a fair and objective indication of safe and reasonable speeds.  Once all of the above are considered a decision will be issued.