The London Transportation Studies Model (LTS)

Transcription

1 The London Transportation Studies Model (LTS) July 2016

2 Contents 3 Introduction 4 Why do we need transport models? 6 TfL s suite of models 8 What is LTS? 11 How was LTS developed? 12 What can LTS be used for? 14 What information can be extracted from LTS? 16 How can I use LTS? 18 More information and contacts Transport for London, October 2014 All rights reserved. Reproduction permitted for research, private study and internal circulation within an organisation. Extracts may be reproduced provided the source is acknowledged. Disclaimer This publication is intended to provide accurate information. However, TfL and the authors accept no liability or responsibility for any errors or omissions or for any damage or loss arising from use of the information provided. 2 Chapter 0 Chapter/Section title here

3 Introduction This document introduces Transport for London s (TfL s) London Transportation Studies Model (LTS). It explains the basic concepts of transport modelling and the role of LTS in the suite of models developed and maintained in TfL Planning. There is also information about the development of LTS, its range of uses and the steps required by anyone who wants to use the model. A more comprehensive set of documents is also available which explain the development of LTS in more detail. In addition, TfL Planning can help with any queries. Contact details are on page 18. The London Transportation Studies Model (LTS) 3

4 Why do we need transport models? Investment in transport can bring about a wide range of economic, social and environmental benefits, both locally and nationally. Introducing new routes, improving highways, building stations and bridges and changing fares and tolls are all investment options that may make it easier for people to move around, or help address the problems of road congestion and public transport crowding. However, with limited financial resources and a variety of potential options, how can we tell which transport improvements are the best to invest in? To answer this, we need to predict the impact of each potential transport scheme on people s travel decisions and the consequent congestion and crowding impacts as London s population and workforce continues to grow and change. Transport models are a source of help and guidance when carrying out such predictions. The decisions that an individual makes when considering travel options can be summarised as follows: Should I live in a place with better transport connections? Do I need to own a car? Shall I travel at all? Which route shall I take? What time of day shall I travel? Where shall I travel to? Which mode of transport shall I use? 4 Why do we need transport models?

5 Transport models are developed to predict some or all of these decisions, with different models often combining to provide an overall picture. They are highly specialised mathematical representations of transport networks that require substantial training to develop the expertise to apply them correctly. TfL s models aim to represent the behaviour of drivers, passengers, cyclists and pedestrians as they negotiate the city s vast transport network. They also show the way transport interventions such as alterations to services and capacity affect travel decisions and the consequent performance of the network. They cover all the main modes of travel including car, taxi, bus, Underground, Docklands Light Railway, London Overground and National Rail as well as freight transport. They help TfL in planning to meet London s future transport needs and identify which transport interventions are likely to be most effective in meeting goals set in the Mayor s Transport Strategy. The London Transportation Studies Model (LTS) 5

6 TfL s suite of models Our models aim to represent all the different decisions that an individual makes when planning a journey. A selection of these models is shown below indicating how data such as demand (the number of trips between each origin and destination) is passed between models. The models described here are often referred to as strategic models, which are used for forecasting the long-term impacts of schemes over wide areas. TfL also owns and operates other models, sometimes known as tactical or operational models, which are used for assessing the short-term impacts. These models include the ONE model and microsimulation models developed using the VISSIM and Legion software packages. This booklet focuses on strategic models only, information on TfL s tactical and operational models is available separately. Planning data Demand Railplan LonLUTI LTS LoRDM Cost of travel Demand HAMs 6 TfL s suite of models

7 The London Transportation Studies Model (LTS): A model which uses population and employment forecasts and other inputs to predict the number of trips to be made in London in the future, where people travel to and from, when they travel and which transport mode they use. The London Land-Use and Transport Interaction Model (LonLUTI): A model which predicts the use of land for different human activities depending on Government policies and transport investment. Railplan Public Transport Assignment Model: A public transport model that predicts the public transport mode (eg. rail, underground, bus) and route that a person chooses to get to their destination, as well as the associated crowding impacts. The Highway Assignment Models (HAMs): Five models covering the whole of London which predict the routes that drivers choose and the associated congestion and delay impacts on London s roads. The London Regional Demand Model (LoRDM) (still under development): A demand balancing model which is similar to LTS but uses the HAMs and Railplan for modelling the choice of route. The London Transportation Studies Model (LTS) 7

8 What is LTS? LTS is a strategic model covering multiple modes of transport across London and its surrounding area. LTS predicts how personal travel in London might respond to changes in population and employment, new transport infrastructure, policy interventions, macroeconomic factors and other influences such as levels of car ownership. It is available for use within TfL and by external stakeholders. The model works in four stages: 1. Estimating how many trips there will be (trip generation) 2. Allocating the trips to mode of transport (mode choice) 3. Determining where the trips come from and go to (trip distribution) 4. Allocating the trips to routes in the highway and public transport networks (trip assignment) The first three stages are carried out in LTS s demand model and the fourth stage in LTS s network assignment models. The transport modes considered in the demand model are car, public transport and walk/cycle. Public transport includes buses, National Rail and Underground (including Docklands Light Railway and London Tramlink), and the highway mode includes a specific assignment of cycling trips. Walk trips are not assigned to the network. LTS represents seven journey purposes for personal travel: Home-based work white collar (journey between home and work by people in socio-economic groups 1 to 3) Home-based work blue collar (journey between home and work by people in socio-economic groups 4 to 8) Home-based employers business (journey between home and work at employers expense) Home-based education (journey between home and school, university or college) Home-based other (journey between home and other activity such as shopping or leisure) Non-home-based employers business (trips at employers expense that do not begin or end at home) Non-home-based other (all other trips) LTS s main strengths are that it can model trip distribution and mode choice, and represent variations in the level of demand based on changes to the cost of travel. LTS uses Greater London Authority population and employment forecasting assumptions to model future demand. LTS, like Railplan and the HAMs, can then assign the trips to the public transport and highway networks which cover the whole of the London area in detail. The images opposite give an idea of the complexity and scale of the model. 8 What is LTS?

9 National Rail Network Underground, DLR and London Tramlink Network Highway Network Bus Network The London Transportation Studies Model (LTS) 9

10 Modelled years and time periods LTS predicts trips for a 24-hour term-time weekday period. It also features detailed assignment models representing average hourly conditions for three key time periods. These periods are: AM Peak (07:00 10:00) Inter Peak (10:00 16:00) PM Peak (16:00 19:00) The model base year is Future year models are available in five-year steps from 2016 to Software and skills LTS has been built using bespoke software on a UNIX platform. A Cube version of the model has also been developed and this is the version of LTS that will be developed further from now on. Using the model requires skills in and experience of UNIX/Cube software and a good understanding of LTS methodology, model assumptions, data preparation and interpretation of results. TfL Planning runs training courses for TfL staff wanting to use LTS. 10 What is LTS?

11 How was LTS developed? The development of LTS began in 1961 with strong links to the London Area Travel Surveys (LATS). These large-scale surveys were repeated every 10 years from 1961 to Since then there has been an annual rolling programme of household surveys known as the London Travel Demand Survey (LTDS). A key feature of LTS is that it is based on extensive data, including household, roadside and public transport surveys and counts. LTS is therefore progressively developed and refined as new survey data becomes available. The current form of LTS emerged in 1998 in the Government Office for London. A review commissioned by TfL in 2006 recommended that LTS could benefit from significant medium-term enhancements. As a result there have been improvements to the highway network (such as updating junction signal timings), new features added including a parking model and cycling assignment, and other enhancements such as updating airport demand. These have culminated in LTS Version 7 which represents 2011 conditions in line with the 2011 Census release. This version is based on the latest public transport surveys and highway data and includes updated networks and modelling assumptions that have been agreed across TfL. LTS Version 7 is available as a UNIX version and in Cube software. It includes an update to the geographical zone base of the model (model zones are used to allocate the start and end points of all trips) to match the higher spatial resolution of TfL s Railplan model. The number of zones has risen from approximately 1,500 to 4,106, with the increase focused on London. Once the 2011 model was finalised, there was a review of forecasting assumptions. The latest population, employment and economic forecasts have been used to produce a set of future year reference cases. LTS is continually developing to meet everchanging needs and policy requirements. Changes to modelling assumptions in LTS can be agreed to meet specific requirements of a study; often this might involve updating economic assumptions or a change to the planning data input to assess the impact of planned development. LTS has been developed with careful adherence to industry guidelines and led or reviewed by experts in the field of transport modelling. In particular, the Department for Transport s Transport Analysis Guidance (WebTAG) was followed to ensure the model is robust and reliable. Experts from consultancies and TfL staff formed a team of experienced transport modellers which has focused on delivering and maintaining LTS to the highest standards possible. Details of the work undertaken have been documented in reports. These reports are available by request. The London Transportation Studies Model (LTS) 11

12 What can LTS be used for? To understand the potential applications of LTS, it is perhaps important to first understand its limitations. Transport models cannot represent accurately every journey made by every person on every network. They are also not precise in the way they replicate individual behaviour and the interaction between vehicles. There are many factors that affect people s travel behaviour and the day-to-day variation in demand and journey times. Even with an extensive set of observed data, these factors are random and impossible to predict. Attempting to develop a model that represents these variations perfectly is unrealistic and is sometimes referred to as over-fitting. Understanding the limitations of a model is vital to making best use of it and taking advantage of its strengths. The reasonable level of expectation from LTS is that it is able to estimate travel demand, the mode of transport chosen and the likely route choices of trips through the highway and public transport networks. It can also estimate changes in total travel and travel patterns in response to large infrastructure schemes, policy changes and planning data changes. LTS is a strategic model used to provide future travel demand data to TfL s other models such as Railplan and the HAMs. These tools may be more appropriate for detailed assessment of changes to infrastructure or services. When LTS is used for a new project it is usually necessary to review the model and the assumptions made to ensure LTS is fit for the purposes required. The table below gives examples of when to use LTS and where appropriate, suggests alternatives. LTS would be a highly useful tool for this study LTS could be used for this study but an understanding of its limitations in this case would be important LTS is not the best tool for assessing the impacts of this study but could provide some supporting analysis 12 What can LTS be used for?

13 Type of study Key strengths of LTS in this case Key limitations of LTS in this case Other tools to consider Summary advice Assessment of new rail or Tube scheme LTS simulates any change in mode choice as a result of a new rail or Tube scheme so the impact on highway and public transport demand can be assessed Consider using Railplan for modelling more localised public transport impacts in greater detail Railplan Assessment of a potential new strategic highway scheme LTS simulates rerouteing and congestion as well as mode shift so the impact on highway and public transport demand can also be assessed Local highway schemes and impacts on minor streets or turning movements at individual junctions would not be well represented HAMs, microsimulation Assessment of overall changes in population, employment and/or economic factors LTS uses population, employment and economic forecasts to simulate the potential changes in highway and public transport demand, mode choice and routes taken It is important to consider local trip rates to ensure a good response TRICS, TRAVL Assessing changes from encouraging the use of public transport LTS simulates shift in mode choice and assesses the impact on highway trips Small changes might not be well assessed in LTS Railplan Assessing the impact of overall predicted traffic growth Additional traffic impacts should be well represented along with any congestionrelated mode shift LTS provides a strategic viewpoint rather than a detailed local assessment HAMs Opportunity Area Planning Framework Assessment of new residential or employment developments Congestion impacts on highway and public transport services, and any changes in route choice should be well represented Impacts on minor streets or turning movements at individual junctions would not be well represented HAMs, Railplan, microsimulation Assessing the impact of a new policy such as car- lite development LTS can predict the impact of lower car ownership and other policies, and predict the effect on public transport Need to ensure careful changes to modelling assumptions and back up work with other research Spreadsheet assessment, behavioural surveys Applying a new toll on a bridge Strategic changes in route choice as well as more localised congestion impacts are modelled in LTS The modelling of new tolls requires some surveys and preparatory work before considering the modelling aspect HAMs, spreadsheet assessment Modelling the impact of a new cycle scheme New cycling matrices have been included in LTS The modelling of cycling is still in its early stages and is a topic of discussion across the industry HAMs Modelling a strategic traffic intervention on a network Strategic rerouting and congestion impacts can be simulated in LTS along with any changes in transport modes used More localised traffic arrangements may not be represented in LTS or may not have a demonstrable impact HAMs, microsimulation Modelling the effect of installing a new pedestrian crossing Changes would be too local to be represented HAMs, microsimulation The London Transportation Studies Model (LTS) 13

14 What information can be extracted from LTS? LTS can be used to extract a wide range of information. LTS highway and public transport demand matrices are used as inputs to Railplan and the HAMs. LTS can also be used to compare a number of modelled scenarios to assess the impact of a transport scheme or development. In the first instance, statistics that indicate overall demand levels by mode of transport can be extracted from the model and analysed. These statistics include: The Top Line Stats spreadsheet includes an overview of the model results and is the first point of call for information Area (London borough and model zone) highway statistics total distance travelled, total time taken, average speed, average vehicle delay Area public transport statistics for each sub-mode numbers for boarding and alighting, crowded conditions, passenger distance travelled, total travel time Highway, public transport and walk/cycle demand matrices number of trip origins and destinations per model zone and mode Highway and public transport network statistics showing route and link information such as capacity, distance and journey time Transport flows crossing defined points, such as river crossings, by direction Demand information by journey purpose 14 What information can be extracted from LTS?

15 Highway Delay Rate (mins/km) 2031 Reference Case, Morning Peak The data can be presented in a variety of different ways such as in tabular or graphical format. A Geographical Information System (GIS) allows the data to be mapped and seen graphically and is a very effective method of presentation. Another important use of LTS is for an economic appraisal of large-scale infrastructure and policy schemes. LTS has an inbuilt economic appraisal module known as Eco2. Information on the number of trips, distance travelled and time taken can be extracted from two model scenarios and used to measure the benefit of one scenario over another in terms of factors such as time savings, fuel costs and the environment. Comparing this to the costs of the scheme being tested can provide an understanding of whether a scheme is worthwhile and how it compares against alternative schemes. The London Transportation Studies Model (LTS) 15

16 How can I use LTS? LTS is available for all types of organisations to use in appropriate studies. This may include use by the London boroughs, other public authorities and private developers, as well as all TfL departments. LTS uses significant computer storage space and so all users log on via remote access to TfL servers. The complexity of the modelling assumptions means TfL has stricter control over LTS modelling than for Railplan or the HAMs. Any model enhancements undertaken for a project should be documented and returned. When LTS is required for use on a project, the project sponsor who commissions the work needs to be licensed to use the model. There is a fee to use LTS. This fee is only for access to the model and there may be additional charges. Details of our current model access fees are available from StrategicModelling@tfl.gov.uk. Licensing The use of LTS is controlled by a licensing arrangement. This is to ensure users have the appropriate expertise needed to enhance and run LTS and interpret the results. 16 How can I use LTS?

17 Typical LTS project life cycle This figure gives an example of a project life cycle that involves the use of LTS. It emphasises the interaction that often occurs between the modelling task and the other appraisal and assessment associated with the project. Timescales on each project tend to vary from a matter of weeks to many months, depending on the scope and complexity. Inception Consideration of modelling work required Consideration of whether LTS or any other models would be appropriate Ensure model accreditation and licensing is in place Implementation of modelling task Carry out a model review and allow time for data collection and/or model refinements if necessary Plan project programme, ensuring that all modelling outputs required for other appraisal and assessment can be provided in good time Allow for iteration with other appraisal and assessment Ensure the required model outputs and analysis are clearly defined Implementation of other appraisal and assessment Plan project programme, ensuring all modelling inputs can be provided in good time Allow for iteration with modelling task Reporting Make use of modelling expertise to ensure model results are interpreted correctly Be clear about the modelling methods used State any limitations associated with the modelling conclusions drawn Review Discuss the project as a whole and its use of the model Consider what went well and what could be improved Return any new versions of the model to TfL at project close The London Transportation Studies Model (LTS) 17

18 More information and contacts For queries about LTS, please contact the Strategic Analysis team in TfL Planning using one of the addresses below: For all general LTS queries For licensing and accreditation queries 18 More information and contacts

19 The London Transportation Studies Model (LTS) 19

20 Transport for London Windsor House Victoria Street London SW1H 0TL July 2016 tfl.gov.uk FL16_099