Advance Traffic Control Signs (W3-1) STOP AHEAD Sign W3-1 (STOP Ahead) sign Here at the Ohio LTAP Center, we have been purchasing roadway signs for Ohio’s Townships for the past five years now, through our Township Safety Sign Grant Program. You can read all about this Grant Program on ODOT’s Office of Local Programs’ webpage. Curve signage and intersection signage have been a major focus for this Grant, mainly because we know that if we can provide Ohio’s townships with the proper signage for their roadways’ curves and intersections, they will likely be able to significantly lower the number of crashes at these locations. Impressive safety benefits from signage improvements have been documented as part of this program (click here for article). One thing we have noticed over these past five years is that a lot of agencies are not aware of the opportunity of providing a STOP AHEAD sign, or dual STOP AHEAD signs, in advance of STOP-controlled intersections. STOP AHEAD signs are intended to reduce the frequency of crashes related to lack of driver awareness of stop control at unsignalized intersections. The purpose of this Technical Brief is to discuss this special warning sign and what some of our ODOT Reference Manuals have to say about its use. So, without further adieu, let’s take a look at this low-cost method of providing motorists with more advance warning as they approach a STOP sign! Winter 2020 The Ohio LTAP Center P a g e | 1 of 10 http://www.dot.state.oh.us/LTAP Introduction to the STOP AHEAD Sign Sometimes, unsignalized STOP-Controlled intersections may be unexpected or may not be visible to approaching drivers because of horizontal or vertical curves or vegetation. Therefore, enhancing the visibility and conspicuity of unsignalized intersections has the potential to reduce the number of crashes associated with drivers' lack of awareness of such intersections. Several studies1 have investigated STOP AHEAD signs, but these studies focused on operational effectiveness. One study investigated STOP AHEAD signs as a means of warning drivers of an upcoming, unexpected, and partially concealed stop-controlled intersection during daytime and nighttime driving conditions2. This study, conducted in 1989, concluded that STOP AHEAD signs do not provide adequate visual stimulus; however the STOP AHEAD sign appears to elicit some limited changes in driving behavior, including lower approach velocities at night and lower longitudinal decelerations near the STOP sign. This 1989 study was conducted when the STOP Ahead sign had a different design. The sign consisted of the words “STOP AHEAD”. Today’s design of the STOP Ahead sign is much different. As you can see, the new design (at the top of page 1) is still a yellow, diamond-shaped sign; however, instead of words it utilizes the image of the shape of a red STOP sign and an arrow pointing up; signifying that there is a STOP sign ahead. This new design paired with a yellow, post-mounted delineator, provides significantly more visual stimulus; even more so if dual STOP Ahead signs are installed. Also, the retroreflective sheeting has been enhanced since 1989. Therefore, the new design of the STOP Ahead sign definitely provides a better visual stimulus to the driver, due to these updates. Illustration of one reason why a STOP Ahead sign should be installed: a vertical curve in advance of the STOP sign that blocks it from the motorist’s view. Source: Pennsylvania DOT – Traffic Engineering Manual. Winter 2020 The Ohio LTAP Center P a g e | 2 of 10 http://www.dot.state.oh.us/LTAP The STOP AHEAD Sign discussed in ODOT Reference Manuals The first ODOT Reference Manual we will search for this sign in is the 2012 edition of the Ohio Manual of Uniform Traffic Control Devices (OMUTCD) (this is the latest edition). It provides standards and guidelines for the use of traffic signs, pavement markings, traffic signals, and other traffic control devices in our state. The OMUTCD applies to any street, highway, bikeway or private roads open to public travel in Ohio; therefore, if YOU are the person in your agency who is responsible for the traffic control devices along your roadways, then YOU need to be familiar with this manual. There are nine Parts in the OMUTCD. Traffic signs are addressed in Part 2 of the OMUTCD. Use of the STOP Ahead (W3-1) sign is discussed in Section 2C.36 Advance Traffic Control Signs (beginning on page 142 of Part 2). This sign is a WARNING sign. As such, they are yellow, diamond-shaped signs. Warning signs call attention to unexpected conditions on or adjacent to a highway, street, or private roads open to public travel and to situations that might not be readily apparent to road users. Warning signs alert road users to conditions that might call for a reduction of speed or an action in the interest of safety and efficient traffic operations. Here is how this sign is addressed in the OMUTCD. Section 2C.36 Advance Traffic Control Signs (W3-1), (W3-2), (W3-3) Standard: 01 The Advance Traffic Control symbol signs include the Stop Ahead (W3-1), Yield Ahead (W3-2), and Signal Ahead (W3-3) signs. These signs shall be installed on an approach to a primary traffic control device that is not visible for a sufficient distance to permit the road user to respond to the device (see Table 2C-4). Support: 02 Figure 2A-4 shows the typical placement of an Advance Traffic Control sign. Winter 2020 The Ohio LTAP Center P a g e | 3 of 10 http://www.dot.state.oh.us/LTAP 03 Permanent obstructions causing the limited visibility might include roadway alignment or structures. Intermittent obstructions might include foliage or parked vehicles. Guidance: 04 Where intermittent obstructions occur, engineering judgment should determine the treatment to be implemented. Option: 05 An Advance Traffic Control sign may be used for additional emphasis of the primary traffic control device, even when the visibility distance to the device is satisfactory. 06 An advance street name plaque may be installed above or below an Advance Traffic Control sign. 07 A warning beacon may be used with an Advance Traffic Control sign. Section 2C.05 of the OMUTCD details the placement of warning signs. Section 2C.05 Placement of Warning Signs Support: 01 For information on placement of warning signs, see Sections 2A.16 to 2A.21 02 The time needed for detection, recognition, decision, and reaction is called the Perception-Response Time (PRT). Table 2C-4 is provided as an aid for determining warning sign location. The distances shown in Table 2C-4 can be adjusted for roadway features, other signing, and to improve visibility. Guidance: 03 Warning signs should be placed so that they provide an adequate PRT (Perception-Reaction Time). The distances contained in Table 2C-4 are for guidance purposes and should be applied with engineering judgment. Warning signs should not be placed too far in advance of the condition, such that drivers might tend to forget the warning because of other driving distractions, especially in urban areas. 04 Minimum spacing between warning signs with different messages should be based on the estimated PRT for driver comprehension of and reaction to the second sign. Winter 2020 The Ohio LTAP Center P a g e | 4 of 10 http://www.dot.state.oh.us/LTAP 05 The effectiveness of the placement of warning signs should be periodically evaluated under both day and night conditions. Footnotes for Table 2C-4 1 The distances are adjusted for a sign legibility distance of 180 feet for Condition A. The distances for Condition B have been adjusted for a sign legibility distance of 250 feet, which is appropriate for an alignment warning symbol sign. For Conditions A and B, warning signs with less than 6-inch legend of more than four words, a minimum of 100 feet should be added to the advance placement distance to provide adequate legibility of the warning sign. 2 Typical conditions are locations where the road user must use extra time to adjust speed and change lanes in heavy traffic because of a complex driving situation. Typical signs are Merge and Right Lane Ends. The distances are determined by providing the driver a PRT time of 14.0 to 14.5 seconds for vehicle maneuvers (2004 AASHTO Policy, Exhibit 3-3, Decision Sight Distance, Avoidance Maneuver E) minus the legibility distance of 180 feet for the appropriate sign. Winter 2020 The Ohio LTAP Center P a g e | 5 of 10 http://www.dot.state.oh.us/LTAP 3 Typical condition is the warning of a potential stop situation. Typical signs are Stop Ahead, Yield Ahead, Signal Ahead, and Intersection Warning signs. The distances are based on the 2004 AASHTO Policy, Exhibit 3-1, Stopping Sight Distance, providing a PRT of 2.5 seconds, a deceleration rate of 11.2 feet/second2, minus the sign legibility distance of 180 feet. 4 Typical Conditions are locations where the road user must decrease speed to maneuver through the warned condition. Typical signs are Turn, Curve, Reverse Turn, or Reverse Curve. The distance is determined by providing a 2.5 second PRT, a vehicle deceleration rate 10 feet/second2, minus the sign legibility distance of 250 feet. 5 No suggested distances are provided for these speeds, as placement location is dependent on-site conditions and other signing. An alignment warning sign may be placed anywhere from the point of curvature up to 100 feet in advance of the curve. However, the alignment warning sign should be installed in advance of the curve and at least 100 feet from any other signs.