Speed table
Encyclopedia
A speed table is a traffic calming
device designed as a long speed hump
with a flat section in the middle. Speed tables are generally long enough for the entire wheelbase
of a passenger car to rest on top. The long, flat design allows cars to pass without slowing as significantly as with speed humps or cushions
. Because they slow cars less than similar devices, speed tables are often used on roads with typical residential speed limits.
Speed tables can also be signed as pedestrian crossing
s.
, concrete
, or rubber
. While traditionally most humps were constructed of asphalt or concrete, rubber is becoming increasingly popular due to several factors. Asphalt and concrete can be difficult to construct precisely while rubber products are pre-shaped to standardized sizes and thus consistently meet industry standards. An additional advantage is ease of installation, which is particularly beneficial when a city wants to test streets before deciding where to keep the devices. The simple installation process also allows for removal during the winter when snow is a concern (preventing damage to the humps by snow plows). In addition, unlike concrete and asphalt, which necessitate frequent and high cost replacement, rubber products are longer lasting and thus more cost-efficient.
Speed cushions are a series of three humps that are ideal for use on streets when emergency vehicle response time is of primary concern
Speed bumps are significantly smaller than speed humps and are used in areas where speed must be slowed nearly to a halt.
Traffic calming
Traffic calming is intended to slow or reduce motor-vehicle traffic in order to improve the living conditions for residents as well as to improve safety for pedestrians and cyclists. Urban planners and traffic engineers have many strategies for traffic calming...
device designed as a long speed hump
Speed hump
A speed hump is a rounded traffic calming device used to reduce vehicle speed and volume on residential streets. Humps are placed across the road to slow traffic and are often installed in a series of several humps in order to prevent cars from speeding before and after the hump...
with a flat section in the middle. Speed tables are generally long enough for the entire wheelbase
Wheelbase
In both road and rail vehicles, the wheelbase is the distance between the centers of the front and rear wheels.- Road :In automobiles, the wheelbase is the horizontal distance between the center of the front wheel and the center of the rear wheel...
of a passenger car to rest on top. The long, flat design allows cars to pass without slowing as significantly as with speed humps or cushions
Speed cushion
Speed cushions are traffic calming devices designed as several small speed humps installed across the width of the road with spaces between them. They are generally installed in a series across a roadway resembling a split speed hump. The design of speed cushions forces cars to slow down as they...
. Because they slow cars less than similar devices, speed tables are often used on roads with typical residential speed limits.
Speed tables can also be signed as pedestrian crossing
Pedestrian crossing
A pedestrian crossing or crosswalk is a designated point on a road at which some means are employed to assist pedestrians wishing to cross. They are designed to keep pedestrians together where they can be seen by motorists, and where they can cross most safely across the flow of vehicular traffic...
s.
Results
Typical speeds resulting from 22 foot speed tables are 20-30 miles per hour. One sample of 8 sites found a 45% decrease in accidents per year with the use of speed tables.Advantages
Speed tables are effective in calming traffic on streets where the speed limit needs to be maintained rather than slowing cars more significantly. Traffic speed, volumes, and accidents have been shown to decrease with the use of tables. Although not as responsive to emergency vehicles as speed cushions, speed tables cause less of a delay than humps and are typically preferred by fire departments over speed humps.Composition
Speed tables can be constructed of asphaltAsphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
, concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
, or rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
. While traditionally most humps were constructed of asphalt or concrete, rubber is becoming increasingly popular due to several factors. Asphalt and concrete can be difficult to construct precisely while rubber products are pre-shaped to standardized sizes and thus consistently meet industry standards. An additional advantage is ease of installation, which is particularly beneficial when a city wants to test streets before deciding where to keep the devices. The simple installation process also allows for removal during the winter when snow is a concern (preventing damage to the humps by snow plows). In addition, unlike concrete and asphalt, which necessitate frequent and high cost replacement, rubber products are longer lasting and thus more cost-efficient.
Similar measures
Speed humps are similar to speed tables although they shorter in length with rounded tops. Humps slow cars more significantly than speed tables.Speed cushions are a series of three humps that are ideal for use on streets when emergency vehicle response time is of primary concern
Speed bumps are significantly smaller than speed humps and are used in areas where speed must be slowed nearly to a halt.