The listed Back to Topics and questions are published to bring about a better general understanding of traffic safety and traffic engineering concepts, and to address some frequently asked questions. These documents reflect the ideals and principals set forth by the Traffic Engineering community at large, and are intended for informational purposes only. These documents may be updated periodically and where applicable, current county ordinances and state laws will prevail. By use of this data the user agrees to hold harmless the County of Riverside and the State of California, including its Officers and employees from any and all liabilities, claims, debts, damages, or actions of any kind arising from said use.
Frequently Asked Questions
What is "Traffic Engineering"?
The Institute of Transportation Engineers, an international professional organization, defines traffic engineering as "that phase of engineering which deals with the planning, geometric design and traffic operations of roads, streets and highways--their networks, terminals, abutting lands and relationships with other modes of transportation--for the achievement of safe, efficient and convenient movement of persons and goods."
When roads and streets were built many years ago, the biggest task facing the road builder was to keep them passable in all types of weather. The problem of moving large numbers of cars and parking them was not significant.
As the number of cars increases, taxing the capacity of our streets and highways, the field of traffic engineering has become increasingly prominent. Each year more people own and operate cars. Urban growth has increased the need for public transportation, for improved movement of goods, for new shopping and industrial centers, and for transportation terminals. Funding for new roads has decreased, due partly to environmental concerns. This has resulted in an increased emphasis on improving the existing road system as much as possible. Traffic engineering is helping to meet these challenges.
Traffic Engineering extends beyond the local level. It plays a vital role in the functional design and traffic operations of the Interstate Highway System. The Traffic Engineer must formulate recommendations for the integration of freeways, shopping centers, and industrial complexes into communities which will serve the population and benefit future development. Traffic Engineers design and operate highway control and communication systems and devise ways to expand capacity and improve safety of existing roads and streets.
Traffic Engineering involves two major areas of activity:
Team decision making about new streets, highways and other transportation matters;
Responsibility for the efficient, convenient, and safe use of existing transportation facilities.
The Traffic Engineer is concerned with groups and individuals and their needs, desires, actions, characteristics, capabilities and limitations as related to the roadway system. His decisions affect drivers, passengers, and pedestrians.
One of the tasks of traffic engineering is long-range transportation planning. Working with sophisticated, computer-aided techniques, engineers and planners determine future transportation needs.
What are the drivers' responsibilities if a traffic accident occurs?
1. Stop.
If you are in an accident while driving, you must stop. If anyone is hurt you must get help.
2. Report the Accident.
If the accident causes injury, death, or property damage of $500.00 or more, it must be reported. Call the local police or the California Highway Patrol. If the accident involves a charge of driving while impaired, an officer will fill out a report. If no report is written by an officer, you must complete an SR22 accident report and submit the report to the Department of Motor Vehicles within 10 days. Your local Police Department or Highway Patrol Area Office will provide you with an SR22 accident form. Keep a copy of the form for you records.
3. Move Your Car If It Is Blocking Traffic.
If your car is blocking the flow of traffic, you must move it. If you cannot move it yourself, you must get help or call a tow truck. This is true anytime your vehicle is blocking the flow of traffic, whether it has been involved in an accident or not.
4. Notification.
If while driving, you hit a vehicle with no one in it or if you damage any object that belongs to someone also, you must tell the owner. Give the owner your name and address in person or in a note attached to the object that was hit. A driver leaving the scene of an accident involving death or personal injury will have his or her license revoked. The driver can also receive a jail sentence.
What can a citizen do to help reduce traffic accidents?
County wide in the County of Riverside, an average of over 17,900 traffic accidents each year account for approximately 245 fatalities, 8,760 nonfatal injuries and over 53 million dollars in property damage. Citizens can do their part to help reduce the high cost of traffic accidents by taking the following actions:
Drive Carefully - Concentrate on driving and use seat belts; do not speed or drink and drive.
Don't Take Chances - Drive safely. Drivers should not try to "beat the light" or "beat the train" at railroad crossings. Drive defensively at all times.
Report Roadway Hazards as soon as possible to city, county or state officials responsible for road maintenance and safety. Roadway hazards that should be reported are:
Traffic signs obstructed by vegetation.
Traffic signal malfunctions.
Traffic signs down or damaged.
Obstructions, potholes, bumps or dips in roadway.
Shoulder washouts.
Water ponding on roadway.
Property Owners should Keep Vegetation Trimmed to insure that good intersection and driveway sight distance is provided and that traffic control signs are visible.
Report Acts of Vandalism to law enforcement, traffic engineering and maintenance officials.
Support Traffic Safety Officials to insure that they have adequate budgets for staff, equipment and supplies to do their job properly.
Turn on Vehicle Headlights between dusk and dawn and anytime visibility is reduced by rain, smoke, fog, etc.
Keep Vehicles in Good Mechanical Condition by regularly checking brakes, tires, wipers and other safety equipment.
Obey Traffic Control Devices such as signs, signals and pavement markings. These devices were installed to enhance safety.
What can a citizen do to help reduce traffic accidents?
County wide in the County of Riverside, an average of over 17,900 traffic accidents each year account for approximately 245 fatalities, 8,760 nonfatal injuries and over 53 million dollars in property damage. Citizens can do their part to help reduce the high cost of traffic accidents by taking the following actions:
Drive Carefully - Concentrate on driving and use seat belts; do not speed or drink and drive.
Don't Take Chances - Drive safely. Drivers should not try to "beat the light" or "beat the train" at railroad crossings. Drive defensively at all times.
Report Roadway Hazards as soon as possible to city, county or state officials responsible for road maintenance and safety. Roadway hazards that should be reported are:
Traffic signs obstructed by vegetation.
Traffic signal malfunctions.
Traffic signs down or damaged.
Obstructions, potholes, bumps or dips in roadway.
Shoulder washouts.
Water ponding on roadway.
Property Owners should Keep Vegetation Trimmed to insure that good intersection and driveway sight distance is provided and that traffic control signs are visible.
Report Acts of Vandalism to law enforcement, traffic engineering and maintenance officials.
Support Traffic Safety Officials to insure that they have adequate budgets for staff, equipment and supplies to do their job properly.
Turn on Vehicle Headlights between dusk and dawn and anytime visibility is reduced by rain, smoke, fog, etc.
Keep Vehicles in Good Mechanical Condition by regularly checking brakes, tires, wipers and other safety equipment.
Obey Traffic Control Devices such as signs, signals and pavement markings. These devices were installed to enhance safety.
What can a pedestrian do to reduce pedestrian accidents?
Each year between 1992 and 1996, there were approximately 380 pedestrian involved collisions in the County of Riverside (county wide). The major accident types most often associated with pedestrian accidents are: Mid-block dart outs; Intersection dash; Vehicle turn/Merge; Multiple lanes crossing; bus sBack to Top related..
Walk Defensively - Be prepared for the unexpected--don't let cars surprise you even if a motorist does something wrong like running a sBack to Top sign or making a sudden turn.
Walk Facing Oncoming Traffic - When there are no sidewalks, walk near the curb, or off the road, if necessary.
Cross Streets at Intersection - Look in all directions before entering the street. Be especially alert to vehicles that may be turning right on a red signal. If there are crosswalks, use them but don't assume you are completely safe in a crosswalk. Don't cross at mid-block because "jaywalking" is dangerous and against the law.
At Intersections, Look for the Signs or Signals - They will help the pedestrian to cross streets safely. Use the push-buttons for crossing protection at signalized intersections that have pedestrian indications. The lighted "Walk" and "Don't Walk" signals are meant for the pedestrian. If the "Don't Walk" light is blinking while you are in the street, continue crossing quickly and carefully. If there are no walk signals, watch the traffic signals. When there are only SBack to Top or YIELD signs, look in all directions and cross when traffic has cleared.
Be Careful in Parking Lots - Pedestrians are supposed to have the right-of- way but many drivers don't wait for pedestrians. Parking lots can be as dangerous as streets. On streets, the direction of cars is usually known but in parking lots, cars might be moving in all directions, including backwards.
Avoid Dangerous Moves - Any movement a pedestrian makes that drivers aren't expecting, could be dangerous. When leaving a school bus, wait a second before crossing. Don't step into traffic from between parked cars since this is a sure way of surprising drivers.
Keep Your View of Traffic Clear at All Times - A pedestrian needs to be able to see cars around him. Don't block your view with packages, umbrellas or other objects.
After Dark, Wear Light Colored or White Clothes - Drivers can see you better if you wear light colored or white clothes. Carry a lighted flashlight and swing it back and forth to improve your chances of being seen by drivers. In spite of the relatively small percentage of pedestrian travel during darkness, more than 38% of pedestrian accidents occurred during dark conditions.
Won't a "traffic signal" reduce collisions at our intersection?
Traffic Signals Don't Always Prevent Collisions. In many instances, the total number of collisions and injuries increase after they're installed.Where signals are used unnecessarily, the most common results are a reduction in right-angle collisions, but an increase in total collisions, especially the rear- end type collision. In addition, pedestrian are often lulled into a false sense of security.
In deciding whether a traffic signal will be an asset and not a liability, traffic engineers evaluate the following criteria:
Does the number of vehicles entering the intersection create confusion or congestion?
Is traffic on the main street so heavy that drivers on the side street will try to cross when it is unsafe?
Does the number of pedestrians trying to cross a busy main street create confusion, congestion or hazardous conditions?
Does the number of school children crossing a street require special controls for their protection? If so, is a traffic signal the best solution?
Will the installation of a signal allow for continuous, uniform traffic flow with a minimum number of vehicle sBack to Tops?
Does an intersection's accident history indicate that a signal will reduce the possibility of a collision?
Does the intersection disrupt desired concentration or organization of a Traffic Flow System, along a major route?
Does the minor street suffer undue delay in entering or crossing the major street during the intersections peak hour(s).
Traffic engineers compare the existing conditions against nationally accepted minimum standards established after many years of studies throughout the country. At intersections where standards have been met, the signals generally operate effectively with good public compliance. Where not met, compliance is generally reduced resulting in additional hazards.
While a properly placed traffic signal improves traffic flow and decreases accidents, an unnecessary one may increase accident potential and can be a source of annoyance to all who use an intersection: pedestrians, cyclists and drivers.
Won't a "children at play" sign help protect our kids?
At first consideration, it might seem that this sign would provide protection for youngsters playing in a neighborhood. It doesn't.
Studies made in cities where such signs were widely posted in residential areas show no evidence of having reduced pedestrian accidents, vehicle speed or legal liability. In fact, many types of signs which were installed to warn of normal conditions in residential areas failed to achieve the desired safety benefits. Further, if signs encourage parents with children to believe they have an added degree or protection (which the signs do not and cannot provide).
Obviously, children should not be encouraged to play in the roadway. The "children at play" sign is a direct and open suggestions that it is acceptable to do so.
Federal standards discourage the use of "children at play" signs.
Specific warnings for schools, playgrounds, parks and other recreational facilities are available for use where clearly justified.
Why are "two-way left-turn lanes" used?
The two-way left-turn lane, a device for increasing capacity and safety, is being more frequently used throughout California and other states. As its name implies, this is a marked lane that is used for left turns by traffic going in both directions on a street. A significant benefit can result when it is used on streets that are lined with commercial development and many driveways.
Despite the initial apprehension which a driver may have, the safety record of these lanes is very good. This may in fact be caused by driver apprehension, as driver's are more cautious. One study showed that where no median was previously provided, the installation of continuous two-way left turn lanes reduced total accidents by about 33% with reductions of 45% and 62% for head- on and rear-end type accidents, respectively.
Another study reported that the "head-on collision," which has been a primary concern among those considering the installation of a continuous two-way left- turn lane, has proved to be an uncommon occurrence and of negligible concern.
Drivers use the two-way turn lane by entering only when they are making the left turn. They do not drive in the lane and therefore do not create a significant potential for head-on collisions. However, by pulling into the left-turn lane when making a turn into a driveway, the driver removes himself from the through lane and this eliminates potential rear-end, side-swipe and lane- changing accidents. These turn-lanes also increase the capacity of the street.
Both Federal and State manuals on traffic control devices specifically provide for the two-way left-turn lane. The markings for the two-way left-turn lanes are yellow and consist of a dashed line and solid barrier line on each side of the lane. The solid line is on the outside of the two-way left-turn lane and the dashed line is on the inside. This marking tells the driver in the through lane that he cannot cross the line for the purpose of passing another moving car. The California Vehicle Code, Section 21460.5(c) prohibits a vehicle from being driven in a designated two-way left-turn for more than 200 feet. The vehicle can, however cross into the lane for the purpose of turning left.
A two-way left-turn lane can change into a single direction left-turn lane at intersections through a change in marking. The lane markings on the right side change from the yellow solid-dashed combination into a standard white lane line used to separate traffic moving in the same direction. The lane markings on the left would change into a double yellow, the standard used to prohibit passing in either direction.
White pavement arrows may be used in addition to the lane and barrier markings to remind drivers that left turns are made in both directions from the lane. Signs may also be used to supplement the pavement markings.
The two-way left turn lane is not a cure-all. However, it is another one of the devices being used by Traffic Engineers to increase the capacity as well as the safety of our existing street system.
How do "traffic signals" work?
When installed under conditions that justify its use, a traffic signal, is a valuable device for traffic control. However, an ill-advised or poorly designed signal is not only annoying, but can be dangerous to pedestrians, cyclists and drivers. Therefore, it is essential that, before traffic signals are installed, engineering studies be made by qualified personnel.
A traffic signal provides alternate right-of-way for different traffic movements at an intersection. It provides a degree of control that is second only to physical barriers. A good general guide is to use the least traffic control required to provide for the safe and efficient movement of vehicles and pedestrians.
Specifications for signals and their placement as well as warrants for their use in the County of Riverside are based on two publications entitled "Manual on Uniform Traffic Control Devices" published by the U.S. Department of Transportation, and the "Traffic Manual" published by the State of California, Business, Transportation and Housing Agency, Department of Transportation.
A signal that minimizes vehicle sBack to Tops and delay also cuts fuel consumption and emissions. The signal controller switches the signal indicates on and off to assign right-of-way correctly and safely. Two basic kinds of controllers are used: pretimed (also known as fixed-time) and traffic-actuated. Pretimed controllers operate on a predetermined, regularly repeated sequence of signal indications. They are used frequently where traffic volumes are predictable and stable.
Traffic-actuated controllers differ from pretimed controllers in that their signal indications are not of fixed length, but change in response to variations in traffic demand. They are frequently used where traffic volumes fluctuate widely or irregularly, or where interruptions to major-street flow must be minimized.
Signal Timing is the division of the cycle into seconds for each of the phases. It assigns right-of-way to alternate traffic movements in order to reduce traffic delay and accident-producing conflicts. Signal timing is constrained by the cycle length - the time for one complete sequence of the signal indications. Cycle length usually fall between 60 and 20 seconds.
There are three common techniques for coordinating traffic signals to operate as a system. This is done to improve the progressive flow of traffic along an arterial street or in a network, any of which can work with either pretimed or actuated controllers.
The simplest system is the basic programmed system in which a master controller simply sends a periodic pulse to all intersections to instruct the local controllers that this is the system reference point. The second method, called "time based coordinators," replaces the central controller and the interconnecting communications completely and places a very accurate timer directly at each location. The third system uses a sophisticated central computer control that exerts more external control on the individual controllers.
How are "speed limits" established in the County of Riverside?
Traffic engineers throughout the country use the normal driver's speed as a guide in setting speed limits since most drivers tend to regulate their own speed according to traffic, road and weather conditions.
For a speed limit to be effective, at least 85 percent of the drivers must voluntarily comply with the law. It is important to remember that the speed regulation informs the driver of the limits in which one can safely operate vehicle under normal circumstances and within the which the driver can be expected to react safely. Setting speed limits at appropriate levels will create a reasonable uniform flow of traffic, discourage violation of the law and help keep streets and highways safe.
"It is common traffic engineering knowledge that most drivers (about 85%) travel at a reasonably safe speed for the various roadway conditions encountered regardless of speed limit signs, but it is for those drivers who don't that the practice of speed zoning does take place for the purpose of providing realistic speed restrictions to which meaningful enforcement can be applied."
"The vehicle speed chosen by a driver is influenced by many factors: the presence of other vehicles, weather, road conditions, road geometrics, adjacent land use, and other factors tabulated in this report. A driver's choice of speed is a balance between expediency and safety, and is often a subconscious reaction to environment."
"Motorists tend to pay little attention to speed regulations which they consider unreasonable unless there is an inordinate degree of enforcement." "Unreasonably low speed limits are commonly violated by a majority of motorists, making enforcement difficult, with resultant operating speeds sometimes higher than would exist with proper, realistic speed limits."
What are the "speed limits" in the County of Riverside?
In the County of Riverside and throughout California, speed limits are governed by the California Vehicle Code, Sections 22348 - 22413. The statutes establish or provides means to establish speed limits by "Blanket Regulations" for special areas on a state wide basis or Prima Facie limits established by state and local agencies through an "Engineering and Traffic Survey".
Basic Speed Law.
Section 22350 of the Vehicle Code provides that " No person shall drive a vehicle upon a highway (including local streets) at a speed greater than is reasonable or prudent having due regard for whether, visibility, traffic, and the surface and width of the highway, and in no event at a speed which endangers the safety of persons or property". The Basic speed law requires that all drivers reduce vehicle speed to a safe speed for existing conditions regardless of the posted speed limit!
70 Mile Per Hour Speed Limits
The Cal-Trans District Director in conjunction with the California Highway patrol and based on engineering standards or an Engineering and Traffic Survey may increase the maximum speed limit from 65 mph to 70 mph to facilitate the orderly movement of traffic, excluding vehicles restricted to 55 mph, as follows:
A Motor truck / trailer with three or more axles or drawing another vehicle.
A passenger vehicle or bus drawing another vehicle.
A school bus transporting any school pupil.
A farm vehicle when transporting passengers.
A vehicle transporting explosives.
A trailer bus.
65 mph Speed Limits
No person shall drive upon a highway at a greater speed than 65 mph unless said highway is posted in accordance with the 70 mph exception stated above.
55 mph Speed Limits
No person shall drive upon a two lane undivided highway at a speed above 55 mph unless post in accordance with the findings of an Engineering and Traffic Survey, and then not to exceed 65 mph.
25 mph Speed Limits
In a School Zone.
In a "Residential" District.
In a "Business" District.
When passing a "Senior Citizen" facility.
15 mph Speed Limits
At a Railroad Crossing with an obstructed view.
At an uncontrolled intersection with an obstructed view.
In an Alley.
Other Speed Zones
Local Authorities (city and county governments) may set speed zones by ordinance declaring a prima facie speed limit as provided in Vehicle Code Sections 22357 and 22358 at 20, 25, 30,35,40,45,50,55, 60 or a maximum speed of 65 miles per hour based on an Engineering and Traffic Survey.
What is an "engineering and traffic survey"?
As defined in the California Vehicle Code, an Engineering and Traffic Survey is a "survey of highway and traffic conditions in accordance with methods determined by the Department of Transportation for use by local authorities." The Survey shall include (but not be limited to) a consideration of the following:
Prevailing Speeds: Speeds are observed and recorded in an unbiased manner in order to determine the normal pace of free flowing traffic under normal conditions.
Accident Records: An analysis of past accident history pinpoints trouble spots and the probable contributing factors in speeding accidents. This process is crucial in the selection of effective countermeasures most likely to correct deficiencies and improve traffic regulations and control.
Highway, Traffic and Roadside Conditions not readily apparent to the driver: A visual inventory of existing roadside conditions, adjacent land use and pedestrian facilities identifies necessary maintenance or improvements and is especially helpful in warning of hidden hazards.
What is the "policy" for curb markings in the County of Riverside?
In order to insure restrictions on parking are installed only where necessary, guidelines have been developed by the County of Riverside Board of Supervisor's , adopted as warrants for Curb Parking Restrictions within Policy G-8, throughout unincorporated areas.
COUNTY OF RIVERSIDE
BOARD OF SUPERVISORS POLICY
Traffic Operational Policies G-8
Curb Parking Restrictions
Red Curb Zones, (No Parking): It is the policy to establish regulations prohibiting parking at locations where such action is necessary in the best public interest for the preservation of public health and welfare or the efficient operation and control of traffic. White Curb: Passenger Loading Zones for the loading and unloading of passengers are only recommended at locations adjacent to points of public assemblage in areas of heavy pedestrian activity and intense parking demand, (adjacent to theaters, hotels, churches, public agencies and curb side mail drop boxes).
Yellow Curb: Commercial loading zones are recommended only at locations where it has been determined that the amount and/or type of loading and unloading in relation to the demand for curb parking is such to cause double parking or result in insufficient commercial access to abutting property.
What are the rules for "disabled persons" parking?
Authority
The State of California Vehicle Code (Section 22511.5) authorizes any disabled person or disabled veteran displaying special identification license plate or placard shall be allowed to park for unlimited periods in the following zones:
- any curb area or parking stall painted in blue
- on streets upon which preferential parking privileges and height limits have been given
- in any parking zone restricted to length of time by sign pursuant to local ordinance
- in any metered parking space without being required to pay
- local authorities, by ordinance or resolution, may designate parking for the exclusive use of disabled person or disabled veteran displaying special identification license plate or placard
Illegal use
The State of California Vehicle code also frowns on illegal use of "Disable Persons Parking" as follows:
It is unlawful to park or leave a vehicle standing in a designated parking space without a disabled person or disabled veteran displaying special identification license plate or placard
It is unlawful to block, obstruct or bar entry to a disabled person or disabled veteran parking stall.
Vehicles may be cited and fined in accordance with local statutes for violations.
Any peace officer or persons hired for parking enforcement may remove any vehicle not displaying the special identification license plate or placard from a "Disabled Persons" designated parking stall and cause the vehicle to be towed at the owners expense.