Display Of Travel Time On Auckland Motorways Variable Message Signs
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Display Of Travel Time
On Auckland Motorways
Variable Message Signs
Human Behaviour, International Practice,
Policy and Customer Perception
September 2010
Authors/ Presenters:
Cormac McBride
BBS (Info Systems), Dip NZ Policing, NZ Cert Intelligence
Analysis, Prince 2 Practitioner, CMILT, IBEC ITS,
EMANZ, Affiliate IPENZ Transportation Group
Transportation Strategist
Traffic Design Group
Email: cormac.mcbride@tdg.co.nz
and
Leon Wee
CPEng, MIPENZ, ME Mgt, BE (Civil)
Principal Project Manager Intelligent Transport System
Highways & Network Operations
NZTA
Email: leon.wee@nzta.govt.nz
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 1 Auckland Motorways Variable Message Signs ______________________________________________________________________________________ ABSTRACT The purpose of developing this paper was to persuade a body of professional opinion that automatic travel time estimates should be displayed on variable message signs (VMS) on the Auckland Motorways. These VMS were initially installed by NZTA to manage incidents reactively. Automated travel time estimates are proactively updated every 30 seconds on VMS on most approach routes to the Auckland motorway network. Once entering the motorway drivers do not receive updated travel time estimates. This is significant because the Auckland motorway environment is constantly changing and incidents may cause significant travel delays within minutes. The approach taken in this paper follows fundamental human behavioural patterns, customer perceptions, the credibility of messages displayed on VMS, international best practice and the applicability of previous research to displaying travel time on VMS within the Auckland Motorway network. The customer focus of this paper finds that relevance and credibility of messages displayed on VMS are critical. The average driver appreciates an accurate expectation of travel time while driving. VMS deliver specific, timely, localised information with a higher level of accuracy than that is achievable on radio. Therefore drivers generally consider VMS to be more useful and reliable than radio or other traditional sources of traffic information. Credible messages are accurate, timely and relevant to the drivers viewing them. Credible messages also convey what the driver does not already know. VMS messages must be noticed by drivers, maximising the time they have to adjust their perception and behaviour. It is better to show no message than an inaccurate or late message. Delivery of accurate current travel time information via VMS is therefore a key feature in credibly managing any congested and fluctuating motorway environment. Used properly, this information enhances the reputation of the operating agency and ensures drivers pay attention to VMS. This paper presents the view of the authors and does not necessarily reflect the official NZTA view. Figure 1: Variable Message Sign (VMS) on Auckland Southern Motorway (State Highway 1) IPENZ Transportation Group Conference Auckland March, 2011
Display of Travel times on McBride, C. & Wee, L. Page 2
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
ABOUT THE AUTHORS:
Cormac McBride is an Intelligent Transport Systems (ITS) specialist with 28 years’
professional transportation experience, both public and private sector. This spans national
strategy, business improvement, corporate ICT, law enforcement and professional driving.
From 2008 he has advised various Australian and New Zealand Government agencies in
expert advisory capacities, including application of technology to the NZ road user charges
system, fleet tracking and collection of data from moving vehicles. He has provided strategic
advice, independent verification, and drafted ITS technical specifications for several major
Australian and New Zealand road projects. Cormac also authored and co-authored a number
of ITS research papers and is the Transportation Strategist at Traffic Design Group.
Leon Wee is the Principal Project Manager – Intelligent Transport System (ITS) for New
Zealand Transport Agency. Leon has over 10 years post-graduate experience in Traffic and
Systems engineering. He holds a Master of Engineering Management (Hons) and Bachelor
of Engineering (Civil). He has been involved with the ramp signalling project since the very
beginning, taking the project from investigation to its current implementation. Leon has also
been actively involved in nation-wide and regional travel demand management (including
ITS) policy and initiatives, traffic engineering design, operations and management. He is
appointed Committee member of the Regional Transportation Systems Management and
Operations with the Transportation Research Board (USA) and Board member for ITS NZ.
Leon has recently been elected as a committee member for the IPENZ Transportation
Group, Auckland Branch.
ABBREVIATIONS USED IN THIS PAPER
AMA Auckland Motorways Alliance
CEN The European Committee for Standardization
CMS Changeable message sign
EJT Estimated Journey Time
FHWA United States Department of Transportation Federal Highway
Administration
ITS Intelligent Transport Systems as applied to
NTCC National Traffic Control Centre (UK)
NZTA NZ Transport Agency
PATH California Partners For Advanced Transit and Highways
TOC Traffic Operations Centre
TxDOT Texas Department of Transportation
TTVMS Travel Time on VMS (UK)
UKHWA UK Highways Agency
VMS Variable message signs
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 3
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
INTRODUCTION
A variable message sign (VMS) is a road sign capable of displaying messages that may be
changed or switched on or off as required to inform drivers of changes in roading conditions.
VMS messages may be reactive incident messages e.g. advance warning of a crash; or
proactive messages e.g. estimated travel time.
NZ and International research1 shows VMS message content has great relevance to drivers,
delivering expectations and warnings in advance. Managing and meeting customer
expectations are key success factors for any business. NZTA is the major provider of travel
information and the sole VMS operator on Auckland Motorways. When noticed, VMS
information supports or modifies driver’s personal travel expectations. VMS on approach to
Auckland Motorways set driver travel time expectations. After a driver enters the motorway
VMS do not display travel time and this is perceived as a gap in customer service.
The potential benefits of displaying travel time messages on existing motorway VMS include
a lower rate of frustration amongst drivers (updated travel time expectations are more likely
to meet overall expectations); reduced average travel times; and more predictable travel
times. There is a propensity for drivers to divert only when a delay exceeds 20 minutes if an
alternative route is available and known to the driver. A lower level of driver frustration
amongst drivers that remain on their original route has obvious safety benefits.
The core issues emerging from this paper are the fundamental characteristics of human
behaviour that cannot be ignored or altered, the consequence to road design, driver
perceptions, and the impact of VMS message credibility.
Fundamental human behaviour remains constant. No matter how we turn over the problem
road user behaviour vs road design, the road owner naturally observes user behaviour based
on existing road design. Therefore the only effective cure for road issues is redesigning the
road environment. VMS messages, display techniques and placement of VMS are critical.
Delivery of accurate current travel time information via VMS is a key feature in credibly
managing any congested and fluctuating motorway environment.
Credible messages are accurate, immediate and relevant to drivers. Credible messages
convey what the driver does not already know. Used properly, this information will both
enhance the reputation of the operating agency and ensure drivers pay attention to VMS.
Credibility is damaged by inaccurate information, advertising and messages that state the
obvious. The types of VMS message that damage credibility include for example a “poor
visibility” message on a sign obscured by mist or a “slippery surface” message on a wet day.
Poor credibility is likely to decrease the attention customers give to VMS, detracting from the
number who subsequently notice or act on incident information. It is better to show no VMS
message than an inaccurate or late message.
The use of VMS to display travel time information while travelling on motorways is
widespread, particularly in the United States and United Kingdom with very positive customer
feedback (89% in UK). Customer perception of NZTA will be positively influenced by
widespread delivery of accurate travel time information on VMS along the Auckland
Motorways adding to the information available on approach to Auckland Motorways.
1
Chen, Carter, Chatterjee, Kronborg, Auckland Motorways Alliance contained in this paper.
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 4 Auckland Motorways Variable Message Signs ______________________________________________________________________________________ UNIVERSAL APPLICABILITY OF RESEARCH - CREDIBILITY Benson, (1996 cited by Lai) stated that a survey of more than 500 motorists in the Washington D.C. region found that demographic variables have little influence on motorists’ attitude toward VMS, except for a few cases involving level of education. Respondents are well disposed to VMS messages that are simple, reliable, and useful. Practical understanding of this finding supports the applicability of international VMS research to other contexts. (NZ) Bierlaire et al (2006) conducted significant research and modelling around the influence of real-time information to driver’s response, this included the display of travel time on VMS. They made a number of conclusions notably that: It appears from the models that the level of error in an information system significantly influences customer perception. It is clear from the examples and discussion throughout this paper that global opinion focuses on the credibility of VMS. Credibility is enhanced by consistently displaying messages that are accurate, timely and relevant to the customers. Display of accurate, automated travel time on “mainline” VMS is widely considered to fit all those criteria and encourages a positive customer perception towards the agency controlling the signs. HUMAN BEHAVIOUR MODEL A good behavioural model has predictive ability and an understanding of cause and effect. Nygardhs and Helmers (2007) conducted an extensive literature review of VMS in European countries, focusing on driver’s behavioural responses to VMS. This included the foundation for a basic behavioural model based on widely cited 1938 research by Gibson and Crooks. Walking, riding a bicycle and driving are all “extensions of ourselves”. Once learnt these extensions become subconscious activities. While driving, we automatically adapt to the current traffic conditions and act based on our individual perception. We perceive that we always keep an adequate safety margin. If our perception of safety fails, we feel feedback in the form of emotional and sometimes physical discomfort. The primary source of information to form individual perception is our three dimensional field of view. A driver’s view includes the geometry of the road, the environmental conditions and the behaviour of other drivers. An experienced driver immediately processes these. A secondary source of information is the symbolic information presented by a road sign (including VMS). Whenever road signs differ from a driver’s strong immediate natural perception, it is natural to question the credibility of the signs. While driving, we divert our conscious skills for handling signs and symbols to other tasks, for example talking to passengers or on mobile phones, listening to the radio, planning or processing work and personal issues. Driving is spontaneous and direct, therefore, drivers must become aware of and consciously recognise VMS before they will read the information displayed. A lack of awareness, through prioritising conscious skills to other tasks will always result in drivers missing the information displayed. The mind naturally filters out factors that it deems irrelevant to the present conscious or subconscious task. IPENZ Transportation Group Conference Auckland March, 2011
Display of Travel times on McBride, C. & Wee, L. Page 5
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
Nygardhs and Helmers state that the three most important conditions that must exist for
drivers to notice signs (rather than subconsciously filter them out) are:
Legibility of the signs and understanding of the message
Relevance of the road sign
Credibility of the road sign
Because the only driving task an experienced driver has to consciously think about is
navigation (planning and route choice), driving tends to remain a subconscious activity.
Subconscious activity tends to follow a task by task pattern, walking step by step, driving turn
by turn. Nygardhs and Helmers comment that crash black spots can normally be described
in terms of a series of complex manoeuvres, one after the other. Drivers operating on a task
by task basis are often not prepared for the next manoeuvre in the sequence.
No matter how we turn over the problem road user behaviour vs road design, the road owner
will naturally observe user behaviour based on existing road design.
However we have no tools for redesigning fundamental human behaviour. The only effective
cure is redesigning the road space (including the way VMS messages are displayed). VMS
are considered an integral part of roading infrastructure by many overseas agencies. Many of
these agencies dedicate 10% of total infrastructure funding to build, operate and maintain
intelligent transport systems (ITS) on all new and existing highways. Application of ITS to
manage traffic effectively is a lower cost alternative than building new or higher capacity
roads.
Critical to this review is the recommendation that messages on VMS must be credible,
accurate and immediate so drivers notice the message and have the maximum time to adjust
their perception and behaviour. It is better to show no message than an inaccurate or late
message.
Human responses to VMS
In trials between major Swedish cities Lund and Malmo which are 20km apart, Daviddson
and Taylor (2003, cited and translated in Nygardhs and Helmers) found that between 6% and
41% of drivers responded to VMS suggesting alternative routes to avoid congestion. It is
suggested that for maximum delay to be managed at least 30% of the drivers needed to
follow the recommendation.
Kronborg (2001) found the compliance with VMS advising alternative routes depends mainly
on the following factors:
How many drivers read the message on the VMS?
How many drivers understood the message on the VMS?
How many drivers trusted the message on the VMS?
How do drivers perceive the traffic situation?
How relevant the alternate route is to drivers?
How accessible do drivers perceive the alternate route is (subject to VMS location)?
How well do the drivers know the alternative route?
What is broadcasted on the radio and other Intelligent Transport Systems? e.g. internet
or recently developed in car navigation units with two way communications.
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 6
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
Kronborg (2001) concluded:
0% to 40% of road users normally choose an alternative route while delay information
is displayed on VMS.
Less or no information is better than an ill founded message e.g. a message about a
past incident.
Messages that motorists find irrational should never be shown e.g. “all traffic exit next
off ramp” (the message doesn’t state why).
Only encourage motorists to deviate from their normal route in order to balance
demand with accessible capacity in rush hours if this favours the individual driver.
The recommended alternative route must result in an evident time saving otherwise
encouragement to deviate may produce credibility problems..
Earlier advance warnings result in greater numbers of drivers diverting.
USA VMS GUIDELINES AND CASE STUDIES
FHWA Guidelines
The US Federal Highways Administration (FHWA) offers a very significant pool of
experience, research and expertise in traffic management procedures. FHWA guidelines on
VMS (known in US as Changeable Message Signs or CMS) are highly relevant to the topic
of this report. The following four subsections are directly paraphrased from the FHWA CMS
Operation and Messaging Handbook.
Credibility of VMS
VMS must be operated credibly to be effective. Paramount to message design and display,
VMS must provide timely, reliable, accurate and relevant information.
Regardless of how well a message is designed, VMS will lose credibility if the messages
displayed are not changed at the correct times and updated to reflect current traffic
conditions. Each time information displayed on VMS is disproved, the credibility of the
system decreases. Eventually the messages are ignored and the VMS system is in jeopardy.
Comment: The Auckland travel time system is near real time, fully automated, updating the
displayed travel time estimates every 30 seconds so does not experience such timing issues.
There are at least eight reasons why message credibility suffers:
Information is inaccurate (e.g., no crash is observed when traffic passes by the location
where an incident was displayed on a VMS).
Information is not current (e.g., the message is not consistent with current conditions).
Information is irrelevant to essentially all motorists using that facility.
Information is obvious by inspection, and hence, is redundant (e.g., displaying heavy
congestion when motorists are driving bumper to bumper in peak traffic).
Information is repetitive (the message is the same each morning when motorists pass
the sign). Displaying the same information on a VMS each day for recurrent congestion
can result in many motorists ignoring the VMS and consequently missing important
messages.
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 7
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
Information is trivial (e.g., drive carefully). Displaying trivial information can result in
many motorists, particularly commuters, ignoring the messages that have no direct
impact on their trips and consequently will begin ignoring the VMS. When an important
message is displayed that will impact their trip, the motorists may not read the
message.
Information is incorrect and can be easily checked and disproved. E.g. Traffic speeds
and inaccurate time to reach a destination are examples of information that can be
easily disproved. Delay time is more difficult for motorists to disprove.
Messages are poorly designed. The information is poorly structured resulting in
messages that are difficult to read and comprehend, or are confusing. The messages
may also contain words that are spelt incorrectly.
FHWA Guiding Policy
Transportation agencies have much more success in operating VMS when they have both
written operations policies, and written operations procedures and guidelines.
VMS operations policies contain the guiding principles that are considered to be prudent and
that influence the actions taken by the managers of Traffic Operations Centres (TOCs) in the
operation of VMS. VMS operations procedures and guidelines outline and describe the day-
to-day operation of the VMSs (e.g., the content and format of VMS messages).
Some agencies have the capability to measure or estimate travel times between sensor
stations and to automatically display travel time information on VMS. The policy is to allow
travel time messages to be displayed during peak and off-peak periods in the absence of
incidents, road works, or other conditions that may adversely affect the driver’s safety or
travel efficiency.
Sample Policy Statement - FHWA Guidelines
Travel time information may be displayed where travel times are measured or calculated
using the electronic sensor equipment on the motorway and in the TOC, and if the
information can be displayed and updated on the VMS automatically by the system
computers.
Justification and/or Considerations
Display of travel time information helps to reduce the amount of time that the VMS are blank
in the absence of incidents or road works.
It is important to recognise that estimated travel times are historic, either current site
conditions (loop detectors) or the travel times of vehicles that recently travelled between two
AVI sensor stations.
Human factors laboratory studies by Dudek et al. (cited by FHWA) suggest that it is
acceptable to use the historical travel times obtained from loop or AVI sensors in VMS
messages.
Results of studies reported in 1979 (cited by FHWA) indicated that the average motorist has
a propensity to divert when a delay on the motorway is 20 minutes or more and earlier
warning results in a greater number of diversions.
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 8
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
The providers of the US VMS traveller information services on VMS do not appear to have
definitive social studies on their impact, or quantifying benefits to consumers or highway
management. Chen (2004) conducted research as part of the California PATH Program into
displaying real time travel times on VMS normally used to communicate information about
traffic diversion, incidents, and delays. Chen (2004) suggests that continued operation of
VMS in the United States indicates widespread acceptance by the public.
CASE STUDIES:
1. San Diego, California, USA
In San Diego, VMS are used to dynamically display automatically generated travel time
information. Traffic Operations Centre (TOC) operators are able to override this with
messages about incidents, road conditions, and events to help drivers choose the best route
and plan for delays.
Chen (2004) concluded VMS “are effective for displaying real time traveller information
because their content has great relevance to their audiences. The most important things for a
driver to know are travel times and alternate routes.”... “The potential benefits of travel time
prediction on [existing] VMS are reduced average travel times and more predictable travel
times.”
Chen (2004) evaluated the improvement in travel time if route choice was based on real time
travel time predictions using historical data. He found potential reductions of 1% - 17% in
average travel times. Chen (2004) accepted that his predictions had errors, but found that
predictions incorporating real time data are much more accurate than predictions based on
historical data alone.
2. San Antonio, Texas, USA - TransGuide
TransGuide provides information to motorists about traffic conditions, such as accidents,
congestion and construction. TransGuide publishes travel times on 220 variable message
signs when not in use for other purposes, on the internet and a Low-Power Television
Station. Partners in the TransGuide project include TxDOT, the City of San Antonio
(Police/Fire/Ambulance/traffic), and Metropolitan Transit.
Carter (2000) found that users of the TransGuide system in San Antonio “consider the
variable message signs to be more useful and reliable than radio or other sources of traffic
information because of the signs proximity to traffic congestion and correspondingly their
higher level of accuracy” This supports Kronborg’s (2001) Scottish findings outlined below.
3. Georgia NaviGator, Atlanta, Georgia, USA
In the late 1980's, Georgian officials began discussing
the concept of ITS to maximize the efficiency of current
and future transportation systems.
The Georgia Navigator is a network of detectors and
message signs built for the 1996 Atlanta Olympic
Games. It computes link travel times using video traffic
detectors and between 6am and 9pm automatically
Figure 2: NaviGator VMS publishes route travel times on VMS and a web page.
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 9
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
Operators can override travel time information when necessary to display incident
information. VMS allow motorists to make informed decisions for themselves by providing a
clear and reliable picture of the road ahead minimising commute times and frustration levels
(supported by Kronborg).
Atlanta is prone to smog between May 1st and September 30th each year (the smog season)
Smog is caused by high humidity, increasing temperatures and a lack of air movement
combined with vehicle and other emissions. Health warnings are common and the VMS are
used to deliver information regarding air quality conditions and air friendly options available
to commuters.
4. Wisconsin DOT, Wisconsin, USA
The Wisconsin DOT study (2004) found that the majority of the Wisconsin motorists reported
the information on VMS was somewhat reliable. Drivers tend to choose alternative routes if
the VMS indicates an increase of travel time of more than 15 minutes, and the delay is due to
a crash, construction, or traffic congestion. The major reason drivers tend to remain on their
travel route is uncertainty whether an alternative route is faster.
UNITED KINGDOM HIGHWAYS AGENCY
Burton et al (2009) stated the UK Highways Agency
(UKHWA) operates Travel Time on VMS (TTVMS)
using upwards of 400 Variable Message Signs. The
TTVMS provides accurate real time predictive traffic
information and has received extremely positive
reactions from road users. The TTVMS service
complements other services delivered to customers
enabling informed travel decisions. Currently there
are 2800 VMS with 459 at key decision points.
Policy driver
The UK Highways Agency aims to deliver safer
roads, informed travellers and reliable journeys. The
network consists of over 8000 Km of English
motorway and major trunk roads.
Figure 3: Mainline VMS in UK
Although this network only comprises 2% of the total English road system, it carries a third of
all traffic and two thirds of all freight traffic.
One target was to reduce average vehicle delay on the worst 10% of journeys compared with
baseline data gathered during previous years. The provision of real-time journey information
to drivers already on the network contributes to meeting this target.
Methodology
The UK travel time system uses a predictive technique rather than just reporting actual
journey times. This is achieved by combining historic data collected by the National Traffic
Control Centre (NTCC) with real-time journey times collected by over 1000 ANPR cameras.
The predicted Travel Times are rounded using pre defined criteria and limited to ensure
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 10
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
compliance with various speed limits including temporary limits at road works. Predicted
Travel Times are calculated and published every five minutes in the format shown in figure 4
below.
Figure 4: Standard UKHWA proactive automated TTVMS messages and reactive delay message
Availability
The service is delivered over as much of the network as the availability of suitable VMS
permits. TTVMS operates automatically and continuously, with a level of reliability and
resilience. Travel Times and Delay Times are published continuously on the VMS unless
these are unavailable due to faults or are being used for the display of higher priority
messages.
Operators are able to monitor system performance, enabling them to override or modify
messages generated by the system.
Benefits of Travel Time VMS
Greater reliability of journey times.
Ability to make route choices en-route.
Increased confidence in VMS settings.
Better information about the reason for and extent of delays reduces frustration for road
users.
The feeling that the road and the road users’ journey is being monitored – an authority
cares about the performance of the route.
Customer Reaction
Surveys were conducted with road users during prototyping to determine reaction to the
service. Additionally the Highways Agency Web site invited feedback. Previous voluntary
feedback to UKHWA generally related to negative experience. In this case website feedback
correlated with the surveys and was 100 times (1000%) greater than the normal level of
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 11
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
feedback. 89% of respondents found travel time information on VMS to be useful or very
useful.
Feedback included comments such as: I've found this a useful indication of exactly how busy
the M6 is and provides me with the option of taking the Toll or A38/A445/A5. It also helps to
reduce stress and uncertainty associated with the usual 'congestion.
The main adverse reactions to TTVMS reported by Burton were:
“It is not possible to complete the journey in the time stated on the sign” – Burton’s
analysis shows that the predicted time was in fact accurate.
“The signs are calculated for a speed of 60 mph regardless of the traffic conditions” –
Burton notes that the signs are dynamic, hence this assertion is not valid.
“It’s foggy and the sign is showing a time which means travelling at 60 mph, which is
not safe” – the signs only display the actual traffic speed regardless of conditions.
“It will encourage people to speed to beat the times” – Burton found no evidence of
this.
“Drivers will slow down to read the signs as they are too complicated” – Burton found
no evidence of this.
Opposing Viewpoint - Chatterjee London Response to VMS
Chatterjee et al (2002) conducted a survey in London determining response to VMS (not
displaying travel time). This survey showed that 80% of drivers considered the information
presented on VMS to be useful, 95% correctly understood the abbreviations. A survey of
drivers' actual responses to a message activation showed that only one third of drivers saw
the information presented to them and 20% of drivers whose survey responses indicated
they should divert did divert, although many found the information useful.
Chatterjee suggested (but did not substantiate) that using London's VMS signs to display
warnings of future disruptions may have reduced their effectiveness contributing to failure to
notice VMS. This suggestion forms the basis for the body of opinion opposing display of
travel times on Auckland Motorway VMS.
Nygardhs and Helmers and the USA FHWA guidelines both provide sound logical
discussions that suggest the degree of attention paid to VMS is somewhat more complex
than suggested by Chatterjee.
De Craen and De Niet (2002 cited in Nygardhs and Helmers) provided a further finding in the
Netherlands that: drivers did not pay much attention to general VMS messages for example
“drive with consideration” and “please be a courteous driver”, however there did not seem to
be any negative road safety effects.
Scotland
Kronborg (2001 cited and translated in Nygardhs and Helmers) found that 82% of drivers
regularly using the VMS road network follow VMS information although it does not agree with
other information channels e.g. radio broadcasts. Kronborg suggested that trust in VMS
indicates both credibility and a hierarchy of trust corresponding with the human behaviour
model discussed earlier in this paper. i.e. Drivers trust their own perception, then VMS then
other information sources.
IPENZ Transportation Group Conference Auckland March, 2011Display of Travel times on McBride, C. & Wee, L. Page 12 Auckland Motorways Variable Message Signs ______________________________________________________________________________________ FRANCE In Paris there are over 350 VMS on the ring motorway. Kronborg (2001) found that 80% of the drivers preferred to be informed of the travel time rather than queue lengths. Another survey conducted in Paris (MV2, 1997 cited by Lai) revealed that: 97% of drivers were aware of the existence of VMS 62% of drivers completely understood the information presented on VMS 84% considered the information presented to be useful 46% had on at least one occasion diverted in response to the travel time information NORWAY In Norway empirical studies were carried out by Erke et al. (2005, cited and translated in Nygardhs and Helmers (2007)). Two VMS sites alternated between blank and road closure with alternative route messages in 15 minute intervals. Around 20% of drivers that would normally choose the closed route changed their route to follow the recommendation. SINGAPORE ITS Singapore and IBM experimented with predictive travel times since 2007 to manage congestion. The results of the experiments have been positive with up to 85% accuracy. Real time traffic information is distributed via VMS (known as travel time displays) on approach to expressways, also via portable/in-vehicle navigation devices, mobile phones and the internet. VMS are also used to display real time electronic road pricing information (ERP) and to display reactive information on the expressways. JAPAN Kronborg (2001) cited investigations in Japan showing that the priority of driver’s decision making process was Experience Feeling VMS Radio information. NEW ZEALAND – NZTA / AUCKLAND MOTORWAYS ALLIANCE The road controlling authority, NZTA entered into a 10 year contract with the Auckland Motorways Alliance (AMA) from October 2008 to operate and maintain the Auckland motorway network. The AMA conducted a customer satisfaction survey prior to the estimated journey time (EJT) VMS being rolled out on approach routes to Auckland motorways. The survey demonstrated that delivery of estimated journey time information during journeys and sufficient VMS to deliver advance warning were of high importance to Auckland motorways customers. Delivery of reliable estimated journey time and access to travel information prior to driving was considered of medium importance. IPENZ Transportation Group Conference Auckland March, 2011
Display of Travel times on McBride, C. & Wee, L. Page 13 Auckland Motorways Variable Message Signs ______________________________________________________________________________________ CONCLUSION Auckland Motorways customers consider both the delivery of travel time estimates during journeys, and a sufficient number of VMS to deliver advance warning, “highly important”. NZTA customers want travel time information delivered to them by VMS. This confirms the applicability of international findings to the Auckland Motorway context. To be effective VMS must be operated in a credible way. Paramount to credibility is message design and display, VMS must provide timely, reliable, accurate and relevant information. Reliable real time automated estimated journey time information such as that available from the proactive, fully automated, Auckland travel time system fulfils all these criteria. Based on the behavioural model outlined in this paper, it is suggested that drivers value credible travel time estimations to reassure their perception of travel conditions, generally enhancing their comfort levels. When incidents occur and reactive information is displayed on VMS driver’s environmental perception is altered and this is likely to influence their behaviour, in route choice, speed and awareness. When accurate, automated, real time motorway travel time estimates are available; that information is generally displayed on “mainline” VMS. This fact is demonstrated clearly by the two nations that arguably have the greatest expertise and influence on New Zealand transport policy (United Kingdom and United States of America). Other international research, particularly Swedish research on human behaviour supports the view that if credible, accurate travel time estimates are available, they should be displayed as frequently as possible to supplement the driver’s natural perception of their environment. Based on international research and best practice, there appears to be strong support for existing “mainline” VMS to display EJT, so long as the estimates displayed are automated, credible and there are no higher priority messages for example incident messages to display. REFERENCES BIERLAIRE, M. AXHAUSEN, M. THÉMANS, K. (2006) Analysis of driver’s response to real- time information in Switzerland http://www.istiee.org/te/papers/N34/02%20bierlaire%20%2021-41.pdf BURTON, P. et al. (2009) The design and implementation of a national real-time travel time on VMS service CARTER, M. (2000) Metropolitan model deployment initiative: San Antonio evaluation report. Technical report, Federal Highway Administration, http://www.itsdocs.fhwa.dot.gov/JPODOCS/REPTS_TE/12883.pdf CHATTERJEE, K., et al. (2002), “Driver Response to Variable Message Sign Information in London”, Transportation Research, Vol. 10C, No. 2, pp. 149-169. CHEN, C. (2004) Travel Times on Changeable Message Signs: Pilot Project, California PATH Research RepUCB-ITS-PRR-2004-5 http://www.its.berkeley.edu/publications/UCB/2004/PRR/UCB-ITS-PRR-2004-5.pdf GEORGIA NAVIGATOR WEBSITE http://www.georgia-navigator.com/about.shtml, HOUSTON TRANSTAR TRAFFIC INFORMATION WEBSITE http://traffic.tamu.edu/aviinfo/avi-tech.html IPENZ Transportation Group Conference Auckland March, 2011
Display of Travel times on McBride, C. & Wee, L. Page 14
Auckland Motorways
Variable Message Signs
______________________________________________________________________________________
IBM (2007) IBM and Singapore's Land Transport Authority Pilot Innovative Traffic Prediction
Tool http://www-03.ibm.com/press/us/en/pressrelease/21971.wss
KRONBORG, P. (2001) VMS för Omledning, Movea Trafikkonsult AB,
http://www.movea.se/vms_omled.pdf
LAI, C. J. YEN, K. T. (2004) Sedan drivers’ attention and response to variable message
signs on freeway in Taiwan, , National Chin-Yi Institute of Technology, Taiwan, ROC
http://www.psychology.nottingham.ac.uk/IAAPdiv13/ICTTP2004Papers2/ITS/Lai.pdf
NYGARDHS, S., HELMERS, G., (2007) Variable message signs a literature review, Swedish
National Road and Transport Research Institute, VTI; Danish Road Directorate.
http://www.vti.se/EPiBrowser/Publikationer/R570ASwe.pdf accessed 27/10/2010
ONE MOTORING WEBSITE (2010) Trial on Traffic Prediction tool
http://www.onemotoring.com.sg/publish/onemotoring/en/on_the_roads/traffic_management/i
ntelligent_transport_systems/traffic_prediction.html
OPERATIONS OFFICE OF TRAVEL MANAGEMENT FEDERAL HIGHWAY
ADMINISTRATION (2004) Changeable Message Sign Operation and Messaging Handbook2
http://tmcpfs.ops.fhwa.dot.gov/cfprojects/uploaded_files/CMS%20Operation%20and%20Mes
saging%20Handbook-Final%20Draft.pdf
PUBLIC TECHNOLOGY.NET (2008) Case study: Highways Agency - Travel Times on
Variable Message Signs team. http://www.publictechnology.net/content/14176
SAN ANTONIO TRANSGUIDE WEBSITE. http://www.transguide.dot.state.tx.us/
SIMLINGER, P. et al. (2008) Proposal on unified pictograms, keywords, bilingual verbal
messages and typefaces for VMS in the Trans European Road Network
http://ec.europa.eu/transport/roadsafety_library/publications/in-safety_d2_3.pdf
SINGAPORE SIGNS
http://www.onemotoring.com.sg/publish/onemotoring/en/on_the_roads/traffic_management/tr
affic_signs.MainPar.26103.File.tmp/Other%20Signs.pdf
TEXAS HIGHWAYMAN PAGES (2010) San Antonio Transguide
http://www.texashighwayman.com/transgd.shtml
UK HIGHWAYS AGENCY WEBSITE (2010) Variable Message signs.
http://www.highways.gov.uk/knowledge/334.aspx
VAN ZWET, E. (2001) A simple and effective method for predicting travel times on freeways.
In 2001 IEEE Intelligent Transportation Systems Proceedings, pages 227–232, Oakland, CA,
2001.
http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fstam
p%2Fstamp.jsp%3Ftp%3D%26arnumber%3D948618&authDecision=-203
WISCONSIN DOT (2004) Evaluation of Variable Message Signs in Wisconsin: Driver Survey
http://on.dot.wi.gov/wisdotresearch/database/reports/45-17variablemessagesigns.pdf
2
Changeable message sign is a term defined in the FHWA publication as “sometimes referred to as variable message signs
or dynamic message signs”.
IPENZ Transportation Group Conference Auckland March, 2011You can also read
