Stop signs and traffic signals are placed at strategic locations to provide safe and efficient movement of the travelling public, including pedestrians. The placement of stop signs and traffic signals are governed by a Federal Government publication: The Manual on Uniform Traffic Control Devices (MUTCD). Worcester follows the Commonwealth of Massachusetts in complying with the MUTCD.
The following are frequently asked questions and the DPW&P response.
One of the most frequent complaints that people have in residential areas is that vehicles constantly speed by the front of their house. They are concerned about the safety of their children. These residents frequently request the erection of additional stop signs. The addition of a stop sign, however, usually does not solve the problem.
A stop sign is an inconvenience to motorists. Because of this, stop signs should only be placed if they meet a Manual on Uniform Traffic Control Devices (MUTCD) warrant. Stop signs are frequently violated if unwarranted. In certain cases, the use of less restrictive measure or no control at all will accommodate traffic demands safely and effectively.
Warrants for a Stop Sign:
Because a stop sign is an inconvenience to through traffic, it should be used only where needed. A stop sign may be warranted at an intersection where one or more of the following conditions exist:
Existing sign installations should be reviewed to determine whether the use of a less restrictive control or no control at all could accommodate the existing and projected traffic flow safely and more effectively.
*Speed, in this warrant is directly related to sight distance and its relationship to vehicles/drivers approaching an intersection.
Many studies have shown that stop signs are not an effective measure for controlling or reducing midblock speeds. In fact, the overuse of stop signs may cause drivers to carelessly stop at the stop signs that are installed. In stop sign observance studies approximately half of all motorists came to a rolling stop and 25 percent did not stop at all. Stop signs can give pedestrians a false sense of safety if it is assumed that all vehicles will come to a complete stop at the proper location. Engineering studies also show that placing stop signs along a street may actually increase the peak speed of vehicles, because motorists tend to increase their speed between stop signs to regain the time spent at the stop signs.
Installing stop signs can do more harm than good. Too many stop signs may also actually discourage good driving habits. Studies have shown that if stop signs are overused or are located where they don't seem to be necessary, some drivers become careless about stopping at them. This can be especially dangerous for pedestrians and bicyclists who may have a false sense of safety from the existence of a stop sign.
Additionally, unwarranted stop sign locations can increase the number of motor vehicle accidents. Studies have shown that stop signs placed where drivers do not expect them can increase the number of 'rear-end' accidents because the average driver does not expect, or anticipate, the need to stop.
Four-way stop signs are not always the answer to reducing intersection crashes. Crash analysis is very complicated and usually identifies multiple causes. Stop signs delay drivers, and many times the drivers become impatient. Impatient drivers may cause crashes. Not all four-way stop intersections are dangerous, but they must be warranted.
The addition of four-way stop control is an inconvenience to all the drivers using the intersection. For this reason, three warrants have been developed and are listed in the Manual on Uniform Traffic Control Devices (MUTCD). A multiway stop control installation may be warranted at an intersection if any of the following conditions exist:
A four-way stop installation should only be used when traffic volumes on the intersecting roadways are approximately equal. However, if volumes are particularly large a traffic signal may be more appropriate. Investigating the warrants listed above will require an extensive traffic engineering study. This study may indicate whether or not a multiway stop control installation is appropriate.
One of the multiway stop control warrants is crash related. If an intersection meets this requirement and it has approximately equal approach volumes, a multiway stop control installation may be warranted for safety purposes. However, the overall results of the traffic engineering study and the professional judgment of the engineer should also be considered. In fact, research has shown that under certain conditions other traffic control measures may be more effective and safer than the addition of a multiway stop sign. A study conducted by the City of Irvine, California, indicated that simply improving intersection visibility can sometimes be a successful approach to crash reduction at intersections.
Justification of signal installation requires considerable data collection and analysis.
The MUTCD lists 11 warrants for the placement of traffic signals. These warrants are summarized below (please refer to the MUTCD for the engineering details). If none of these warrants are met, a traffic signal should not be placed. In addition, the fulfillment of a warrant or warrants also does not in itself justify the installation of a signal.
Installing a traffic signal at a low-volume intersection can significantly increase crashes and delays.
Again, the increase in delay and stops then translates into higher fuel consumption, increased travel times and higher point source pollution. The length of delay is directly related to a number of factors. Cycle length is one factor, for example, that is influenced by traffic volumes and the need to safely accommodate pedestrians. The pedestrian crossing time constraints could significantly increase the necessary cycle lengths.
Although traffic signals can reduce the total number of collisions at an intersection, research has shown that certain types of crashes (e.g., rear-end collisions) may actually increase after a signal is installed. For this reason, the type and number of crashes at an intersection should be considered before the installation of a signal.
Traffic signals can represent a positive public investment when justified, but they are costly. A modern signal can cost $150,000 to $200,000 to install. In addition, there is the cost of the electrical power consumed in operating a signalized intersection 24 hours a day and general maintenance.