All-way stop

A 4-way stop

An all-way stop or four-way stop is an intersection system used predominantly in the United States of America, Canada and South Africa where traffic approaching it from all directions is required to stop before proceeding through the intersection. An all-way stop may have multiple approaches and may be marked with a supplemental plate stating the number of approaches.

Operation

A motorist approaching an all-way stop is always required to come to a full stop before the crosswalk or stop line. In most jurisdictions that use all-way stops, pedestrians always have priority at a crosswalk, even if the crosswalk is not delineated with pavement markings. Within some US jurisdictions, such as the state of Idaho, bicyclists are exempt from the need to make a complete stop, but must give way to other vehicles as otherwise required by law. After a full-stop has been made, vehicles usually have the right-of-way to proceed through the intersection in the order that they arrived at the intersection. In the USA, if vehicles arrive at approximately the same time, each driver must yield to the drivers on their right, while in South Africa drivers must use common sense and make eye contact and gestures. Some areas have additional formal and informal rules which may or may not include special procedures for when all stop signs are approached simultaneously.

Application

File:4 Way.svg   File:All way.svg

In the USA the Federal Highway Administration's Manual on Uniform Traffic Control Devices (MUTCD) defines the standards commonly used for the application of all-way stops. Where a stop has been determined to qualify, it is signed at all intersections with a standard octogonal "Stop" sign, with one of two secondary signs placed below the stop sign. In the case of an intersection with 4 points, optionally a "4 Way" secondary sign may be placed below the stop sign. An "All Way" secondary sign may be placed at a 4-way stop, and an "All Way" secondary sign only must be used where there are other than four points meeting at the intersection and all points have a stop sign. According to the MUTCD, installation of an all-way stop should be based on a traffic engineering study to determine if minimum traffic volume or safety criteria are met. These intersections are often found where roads with considerably equal traffic levels meet each other but the overall level of traffic present at the intersection does not justify a traffic light, and or in a location where the right of way was otherwise unclear. An all-way stop may also be justified if the intersection has a demonstrated history of crashes in a given period of a type susceptible to correction by installing an all-way stop. All-way stops may also be used as an interim measure preceding the placement of a traffic light, to provide a low-speed area for pedestrians to cross, where a cross street experiences considerable difficulty finding safe gaps due to heavy traffic volumes, or where traffic is frequently delayed by turning conflicts. Additionally the MUTCD advocates the placement of all-way stops at intersections between through roads in residential areas if an engineering study can show that traffic flow would be improved by installing the all-way stop control. Despite published guidelines, all-way stops are routinely placed by jurisdictions due to political pressure from adjacent residents. Intersections between two minor highways with similar traffic counts, two collector roads in an urban or suburban setting or a collector road and a local road in a busy setting (such as near a school) are the most common locations for an all-way stop.

Traffic signals will sometimes flash red indications in all directions following a malfunction, or all-red flashing operation may be scheduled to reduce delay or handle construction activity or unusual traffic patterns. When a traffic signal flashes in all-red mode, it legally operates as an all-way stop. When all approaches to an intersection are controlled in this way the rules for an all-way stop apply. However, it must also be noted that traffic signals may also flash yellow to major directions and flash red to minor directions during off-peak times to minimize traffic delays, in which case only side-street traffic is required to stop and yield the right of way to crossing traffic on the major street.

During electrical outages when a traffic signal does not display any indications including flashing red, some jurisdictions require that the intersection be treated as an all-way stop. Other jurisdictions treat a dark signal as an uncontrolled intersection, where standard rules of right-of-way apply without the requirement of a complete stop.

Benefits and disadvantages

The main reason for the use of stops signs at road junctions is safety. According to an international study of locations where the system is in use, all-way stop control applied to four-legged intersections may reduce accident occurrence by 45%. However, given alternative methods of intersection control and some of the disadvantages of all-way stops, the Handbook of Road Safety Measures recommends that four-way stops are best used between minor roads away from urbanized areas. Some of the other benefits of all-way stops are:

• equal priority for all approaches, which can reduce delays to side-street approaches that would otherwise need to wait for a safe gap.

• assurance that vehicles enter the intersection at a low speed and have more time to take heed of the traffic situation, especially useful when sight distance is highly restricted.

• provision of a low-speed crossing point for pedestrians.

• often used as the default behaviour when traffic signals fail, allowing a reasonable traffic flow.

Some of the disadvantages associated with all-way stops are:

• increased emissions of hydrocarbons.

• increased average delay.

• that once installed stop signs in general are unsafe to remove, accidents that result in injury may increase by 40%. Once an all-way stop is installed, removal is difficult and risky, as habitual drivers may continue to expect an all-way stop condition.

• wasted fuel and vehicle wear by requiring all drivers to stop, even when conflicting traffic is not present.

• worsened delays at adjacent intersections by causing traffic to leave the intersection equally spaced.

• obstructions to traffic that would not otherwise exist, increasing the risk of rear-end crashes.

• reduced respect for stop signs if drivers perceive a complete stop to be unnecessary in the absence of conflicting traffic.

Worldwide comparisons

Most countries outside North America, particularly in Europe, rarely have intersections where all users must stop at all times; the conditions for stop sign placement may preclude such an arrangement in many places. In Sweden all-way stops (Flervägsstopp) have been tested since the 1980s but are little used even though they are now permitted.

At four-legged intersections within Europe, it is usual for one road to be given priority over the other, or for a roundabout or mini-roundabout to be used to assign a relative priority to each approach. (This latter solution remains rare in North America, where early failures of rotaries and traffic circles caused such designs to lose favour until the gradual introduction of the modern roundabout in the late 20th century.)