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Active traffic management (also managed lanes, smart lanes, managed/smart motorways) is a method of increasing peak capacity and smoothing traffic flows on busy major
highway A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-access ...
s. Techniques include variable speed limits, hard-shoulder running and ramp-metering controlled by overhead
variable message signs A variable- (also changeable-, electronic-, or dynamic-) message sign, often abbreviated VMS, CMS, or DMS, and in the UK known as a matrix sign, is an electronic traffic sign often used on roadways to give travelers information about special ...
. It has been implemented in several countries, including
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...
, the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...
and the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
.


United Kingdom

It is currently in operation on the
M42 motorway The M42 motorway runs north east from Bromsgrove in Worcestershire to just south west of Ashby-de-la-Zouch in Leicestershire, passing Redditch, Solihull, the National Exhibition Centre (NEC) and Tamworth on the way, serving the east of the Bi ...
south-east of
Birmingham Birmingham ( ) is a city and metropolitan borough in the metropolitan county of West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1.145 million in the city proper, 2.92 million in the We ...
and in
Warwickshire Warwickshire (; abbreviated Warks) is a county in the West Midlands region of England. The county town is Warwick, and the largest town is Nuneaton. The county is famous for being the birthplace of William Shakespeare at Stratford-upon-Avo ...
. The scheme had initially been criticised by some due to possible safety and environmental concerns, however a
Highways Agency National Highways, formerly the Highways Agency and later Highways England, is a State-owned enterprise, government-owned company charged with operating, maintaining and improving Roads in England, motorways and major A roads in England. It al ...
report into the first six months of the scheme showed a reduction in the number of accidents from over 5 a month to 1.5 per month on average. it has now been expanded onto other roads following the initial
evaluation Evaluation is a systematic determination and assessment of a subject's merit, worth and significance, using criteria governed by a set of standards. It can assist an organization, program, design, project or any other intervention or initiative to ...
on the M42. It is seen as a less expensive alternative to road widening.


Technology

The section of road subject to ATM is monitored by
MIDAS Midas (; grc-gre, Μίδας) was the name of a king in Phrygia with whom several myths became associated, as well as two later members of the Phrygian royal house. The most famous King Midas is popularly remembered in Greek mythology for his ...
sensor loops placed in the road every (which is closer than normal) to observe traffic flows. A computerised system monitors the traffic flows and can set the best speed limit for the current flow of traffic and switch on speed limit signs mounted on gantries up to before an incident. Operators can also monitor 150
CCTV Closed-circuit television (CCTV), also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly ...
cameras along the route and can control both the speed limits and information signs. Overhead
variable message sign A variable- (also changeable-, electronic-, or dynamic-) message sign, often abbreviated VMS, CMS, or DMS, and in the UK known as a matrix sign, is an electronic traffic sign often used on roadways to give travelers information about special ...
s can direct drivers to use the hard shoulder during busy periods. When the speed limit has been lowered to or below the hard shoulder can be opened as an additional lane. To facilitate this and still maintain safety a series of refuge areas have been created around every along that stretch of the road. These take the form of lay bys to the side of the hard shoulder and contain the SOS phones within them. In the event of a vehicle breaking down on the hard shoulder, operators can close it or they can close a lane to allow
emergency service Emergency services and rescue services are organizations that ensure public safety and health by addressing and resolving different emergencies. Some of these agencies exist solely for addressing certain types of emergencies, while others deal w ...
s access to an
accident An accident is an unintended, normally unwanted event that was not directly caused by humans. The term ''accident'' implies that nobody should be blamed, but the event may have been caused by unrecognized or unaddressed risks. Most researche ...
. The hard shoulder is never opened on the sections under a junction between the off and on slip roads. Close to junctions use of the hard shoulder as a lane is restricted to traffic exiting or entering at that junction. ATM involves converting the
hard shoulder A shoulder, hard shoulder (British) or breakdown lane, is an emergency stopping lane by the verge of a road or motorway, on the right side in countries which drive on the right, and on the left side in countries which drive on the left. Many wid ...
into a normal lane during periods of high traffic flow to expand the capacity of the road and may reduce the need to widen motorways. Similar schemes have already been implemented in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
. The system makes use of
Automatic Number Plate Recognition Automatic number-plate recognition (ANPR; see also other names below) is a technology that uses optical character recognition on images to read vehicle registration plates to create vehicle location data. It can use existing closed-circuit tel ...
cameras which to monitor traffic flows and tailor the system. Digital enforcement cameras are also mounted on the gantries and are operated by the
West Midlands Police West Midlands Police is the territorial police force responsible for policing the metropolitan county of West Midlands in England. The force covers an area of with 2.93million inhabitants, which includes the cities of Birmingham, Coventry, ...
to enforce the mandatory variable speed limits.


Future implementation

*
Vehicular Ad-Hoc Network Vehicular ad hoc networks (VANETs) are created by applying the principles of mobile ad hoc networks (MANETs) – the spontaneous creation of a wireless network of mobile devices – to the domain of vehicles. VANETs were first mentioned and intro ...

Intelligent Traffic-light Management


In the United States

A number of highways in the United States have
variable message sign A variable- (also changeable-, electronic-, or dynamic-) message sign, often abbreviated VMS, CMS, or DMS, and in the UK known as a matrix sign, is an electronic traffic sign often used on roadways to give travelers information about special ...
s and variable speed limits. The
New Jersey Turnpike The New Jersey Turnpike (NJTP) is a system of controlled-access highways in the U.S. state of New Jersey. The turnpike is maintained by the New Jersey Turnpike Authority (NJTA).The Garden State Parkway, although maintained by NJTA, is not cons ...
has been using active signage since the 1960s, though systems have evolved over time as they have been deployed in other areas of the country. A modern implementation of active traffic management was activated in 2010 using
IRIS Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...
on Interstate 35W in
Minneapolis, Minnesota Minneapolis () is the largest city in Minnesota, United States, and the county seat of Hennepin County. The city is abundant in water, with thirteen lakes, wetlands, the Mississippi River, creeks and waterfalls. Minneapolis has its origi ...
and its southern suburbs as part of the Urban Partnership Agreement. Active lane management on I-35W was later combined with
high-occupancy toll lane A high-occupancy toll lane (or HOT lane) is a type of traffic lane or roadway that is available to high-occupancy vehicles and other exempt vehicles without charge; other vehicles are required to pay a variable fee that is adjusted in response ...
s and eventually joined by a bus rapid transitway. An ATM scheme was deployed on 10 August 2010 in
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
.


In Washington State

The Washington State Department of Transportation (WSDOT) has completed Active Traffic Management schemes on several motorways in the Seattle metropolitan area. It is the first legally enforceable system in the United States. Failure to comply with speed limits and overhead instructions are citable offences. ATM systems were activated on of the I-5 northbound carriageway in August 2010. In November 2010, ATM was expanded to of the SR 520 in both directions. In March 2011, ATM completed testing and began operations on of the I-90 in both directions. The ATM schemes build upon WSDOT’s existing arsenal of Intelligent Transport Systems (ITS) which is supported by traffic sensor loops embedded in the pavement approximately every 800 m (2640 ft) apart. On motorway sections with ATM, gantries are also spaced roughly 800 m (2640 ft) apart. The primary ATM strategies used by WSDOT is ramp metering, queue protection, hard shoulder running, junction control, and lane-specific signalling. Motorway operations in the Seattle area are conducted in the Northwest Region Traffic Management Centre in Shoreline, just north of Seattle.


Ramp metering

WSDOT’s ramp metering strategy is aimed at reducing the volume of traffic entering the motorway and has been in operation since the early 1980s. Traffic signals are operated part-time on slip roads, which are used to temporarily store traffic. The queuing traffic is then released onto the motorway one vehicle per signal cycle. Unlike other states in the U.S., WSDOT does not have a time-of-day schedule for metering, nor does it have a rigid meter rate as it is considered too inflexible. Dedicated operators monitor traffic conditions visually through CCTV and switch the meters on and off manually. Once turned on, the meter rate is automatically determined and updated every 20 seconds using a local traffic-responsive algorithm based on fuzzy logic. The algorithm, named the Fuzzy Logic Ramp Metering algorithm, is the successor to the Bottleneck Algorithm. The length of the queue on the slip road and the mainline occupancy immediately surrounding the slip road are fed as inputs to the algorithm, which determines a meter rate that allows as few vehicles to join the motorway mainline as possible without overflowing queuing vehicles onto nearby arterial streets. During its operation, ramp metering is fully automated. Operators will manually tune the ramp meters if necessary. They also have the ability to intervene when a malfunction occurs. The performance of Fuzzy Logic Ramp Metering is comparable to the ALINEA algorithm used by several European agencies.


Queue protection

Variable speed limits displayed on overhead lane control signs (LCS) above each lane are used to reduce traffic speed prior to a congestion point. Variable message signs (VMS) accompany the reduced speed limit to warn drivers of slow traffic. Speeds are determined automatically and are lowered using one or two upstream gantries depending on the size of the reduction. Intervals of 8.0 km/h (5.0 mph) and 16.1 km/h (10.0 mph) are common. Upon the end of a congestion point, speed limits are returned to the default speed. The primary purpose of queue protection is to reduce rear-end collisions.WSDOT - New Technologies for Fighting Congestion


Hard shoulder running and junction control

As part of the SR 520 Bridge Replacement and HOV scheme, WSDOT plans to implement junction control through hard shoulder running. Based on traffic conditions, ATM will open the shoulder as an auxiliary lane on the SR 520 westbound carriageway across Portage Bay Bridge, which will turn the motorway section from a 3 + 2 to a 3 + 3 dual carriageway. The additional capacity will allow traffic from the Montlake Boulevard junction more room to merge. The shoulder running can also be activated for incident management. A similar scheme is being developed for the I-5 northbound carriageway in Marysville.


Lane specific signalling

In the event of a lane closure due to a collision or roadwork, LCS signs will display a red X above the closed lane at the location of the incident. The gantry immediately upstream will direct motorists to merge into adjacent lanes. Drivers are allowed approximately 800 m (2640 ft), or one gantry interval, to clear the lane. Lane closures are done manually through operator intervention. Operators also have the ability to override HOV designation above HOV lanes, opening it to regular traffic if necessary.


Implications

Although WSDOT has not published data on the performance of the ATM implementation, low compliance with variable speed limits and overhead instructions is noticeable among Washington drivers. Part of the challenge is allowing drivers more time to adapt to the system, while the other part is poor enforcement from the Washington State Patrol and the absence of automated enforcement such as those used in England.


See also

*
Traffic optimization Traffic Optimization are the methods by which time stopped in road traffic (particularly, at traffic signals) is reduced. Need for traffic optimization Texas Transportation Institute estimates travel delays of between 17–55 hours of delay per ...
* Speed limit: Variable speed limits * Variable-message sign


References

{{Reflist, 2


External links


Details of the ATM scheme

Active Traffic Management in detail

View live Motorway CCTV Cameras in the UK

Explanation of the ATM scheme



SCATS Sydney Coordinated Adaptive Traffic System

Atlas Traffic Management
Road traffic management Intelligent transportation systems Road transport in the United Kingdom