Thursday, September 24, 2015

A Complex Network Perspective for Characterizing Urban Travel Demand Patterns

Recent Working Paper:

Saberi, M., Hosseini, A., Mahmassani, H., Brockmann, D. A Complex Network Perspective for Characterizing Urban Travel Demand Patterns. [Working Paper]
Urban travel demand, consisting of millions of origin-destination trips, can be viewed as a large-scale network. The paper introduces a complex network-motivated approach to understand, characterize and model urban travel demand patterns. We compare selected network characteristics of travel demand patterns in two cities, presenting a comparative network-theoretic analysis of Chicago and Melbourne. The proposed approach develops an interdisciplinary and quantitative framework to understand and model dynamical aspects of mobility in urban areas. Statistical properties of the complex network of urban trips of the selected cities are explored. We show that travel demand networks exhibit similar properties despite their differences in topography and urban structure. Results suggest that the underlying dynamical processes in travel demand networks are similar and evolved by the distribution of activities and interaction between places in cities. Results provide a first step towards a new methodological base for calibration and validation of agent-based travel demand models.

Thursday, September 17, 2015

Exploring the Effects of Land Use, Travel Behavior, and Socio-Economic Characteristics on Safety at the Planning Level: Empirical Evidence from Melbourne

Recent Working Paper:

Amoh-Gyimah, R., Saberi, M., Sarvi, M. Exploring the Effects of Land Use, Travel Behavior, and Socio-Economic Characteristics on Safety at the Planning Level: Empirical Evidence from Melbourne. [Working Paper]
Understanding the relationship between road crashes, traffic, socio-economic, and land use characteristics is necessary in evaluating the safety impacts of urban policies at the planning level. The aim of this paper is to provide further empirical evidence on the significance and magnitude of various planning factors that influence transportation safety at the network level. We estimate multiple Negative Binomial (NB) regression models to explore the impact of different planning factors, individually and combined, at different geographical levels. Results suggest that vehicle kilometers traveled (VKT), percentage of population cycling to work, percentage of households with low income, and land use balance mix index significantly influence number of crashes. We also show that using different spatial units could produce different modeling outcomes, as expected. The study is a first step towards integration of safety modeling into the transportation planning.

Forecasting Vehicle Kilometers Traveled: Estimating an Autoregressive Integrated Moving Average Model (ARIMA) with Exogenous Variables

Recent working paper:

Nazemi, M., Shafiei, M.S., Saberi, M., Sarvi, M. (2015) Forecasting Vehicle Kilometers Traveled: Estimating an Autoregressive Integrated Moving Average Model (ARIMA) with Exogenous Variables. [Working Paper]
Vehicle kilometers traveled (VKT or VMT) is a key variable in long-term transportation planning and policy making, especially for road infrastructure investment. In this paper, we estimate an Autoregressive Integrated Moving Average (ARIMA) model with exogenous variables to forecast VKT in Australia. The estimated model produces forecasts based on lagged values in the time series and the errors made by previous predictions, which typically allows the model to rapidly adjust for sudden changes in trend, and at the same time includes exogenous variables resulting in more accurate forecasts. We found that the effects of unemployment rate, fuel price over Gross Domestic Product (GDP) per capita, and Consumer Price Index (CPI) on VKT are all statistically significant and negative. More importantly, number of vehicles per capita appears to be highly statistically significant with positive impact on VKT. We postulate that policies or behavioral changes towards less car ownership are more likely to have greater impact on VKT rather than fluctuations in fuel price, unemployment rate, or individual’s purchasing power.

Sunday, September 6, 2015

GovHack 2015: 1st Prize in Best Data Journalism Hack

I am happy to announce that my group (Monash City Science) is awarded the 1st prize in Best Data Journalism Hack in GovHack 2015 for the project "Mapping Pedestrian Activities and Safety in Melbourne."

In the project, we analyzed and visualized the relationship between pedestrian activities and safety over time in City of Melbourne using combined pedestrian count sensors data and pedestrian crash statistics.

Special thanks to Julian, Bryan, Emily, and Sajjad for being part of the Monash City Science team.

UPDATE 1: Here is a video from the award ceremony. Watch @38:57.

UPDATE 2: Photo with award sponsors ABC Australia and Australian Taxation Office

Wednesday, September 2, 2015

3D modeling with 123D Catch app

Here is a 3D model of mine sitting on a chair in the class. We built this on the spot in ENG1021 (Spatial Communication in Engineering) class today. The 3D model is built from more than twenty 2D pictures taken by a cell phone/mobile camera. Not too bad, ha? Make sure you click on "3D view".

The 3D model is built using an image-based technology, 123D Catch app: 
It's a free app. So don't expect a powerful matching algorithm here.

Tuesday, September 1, 2015

Historic Papers on Network Traffic Flow Theory (NFD/MFD)

Here is a list of historic papers on network traffic flow theory which is currently known as Macroscopic Fundamental Diagram (MFD) or Network Fundamental Diagram (NFD). Thanks to the Northwestern University Transportation Library, I managed to get a scanned copy of the papers. Click on the title of each paper to view the scanned PDF.

  • Mahmassani, H.S., Williams, J.C., Herman, R., 1984. Investigation of network-level traffic flow relationships: some simulation results. Transportation Research Record: Journal of the Transportation Research Board, No. 971, 121-130.
  • Mahmassani, H.S., Williams, J.C., Herman, R., 1987. Performance of urban traffic networks. Proceedings of the 10th International Symposium on Transportation and Traffic Theory, Elsevier Science Publishing, 1-20.
  • Williams, J.C., Mahmassani, H.S., Herman, R., 1987. Urban traffic network flow modelsTransportation Research Record: Journal of the Transportation Research Board, No. 1112, 78-88.