Ahmad Omran, Transport Planner

How do you conduct a traffic impact study to improve the level of service and the efficiency of future public transport projects?

 

 

 

My project’s objective was to conduct a traffic impact study for King Saud University Endowments Project in Riyadh (KSUE), in Saudi Arabia, taking into consideration all the landuses and background traffic for the whole university, where the number of students and therefore trips has gone up in recent years, and where additional facilities attracting even more people are currently under construction. The study had to include the current and future facility projects in the area, in addition to the significant changes in the vicinity, roads’ and intersections’ configurations and transport modes. The study had to fulfil several requirements, among others take into consideration the public transport strategy in the surrounding area and create the access and egress strategy for a smooth traffic circulation with minimal congestion including mitigation measures to improve the level of service and reduce delays.

 

Collecting and analysing the data
At first, I analysed the project location to set the boundaries for the study area and have a close look at the pedestrian accessibility of the site and the different major roads. In order to capture the existing traffic volumes on the roadway network, including the turning movement volumes at the intersections in addition to signal timing and phasing, I collected data from various sources and surveys: vehicle classified automatic traffic counts, turning movement counts, video mapping of the road network, existing road inventory, site access and egress points, phasing and timing schemes of existing traffic signals, surrounding public transport systems and side parking and queuing.
Based on the Highway Capacity Manual, I evaluated the prevailing traffic conditions using the analysis software, PTV Vistro for intersections and PTV Visum for a volume-to-capacity check after having coded the existing network. To find out how the future road network and traffic analysis zones look like, I modelled all the project network elements with PTV Visum and coded all the characteristics. I then used the four-step travel demand forecasting to determine the trip generation, trip distribution, mode choice and travel assignment. Since the project is located in Riyadh, I adopted the city’s Trip Generation Manual and the trips were divided between internal to internal trips, internal to external trips, external to internal trips and external to external trips between the different coded traffic analysis zones. As for the mode choice, since no data regarding the public transport system was available, the local authorities advised to consider a share of 20% for all public transport systems. The trip assignment is the last step, where I obtained the resulting peak hour traffic flows on the various roadway links based on a LUCE assignment.
To better map out how a future road network should look like, I used PTV Vistro to evaluate the delays on the key intersections within the study area, based on the existing intersections layouts and signal timing and phasing programs. Based on the analysis results, I proposed mitigation measures on a macroscopic level changing the road geometry and proposing additional accesses, and on a microscopic level, optimising traffic signals and changing intersection configurations.
The last aspect of my study was about evaluating the provided parking spaces and comparing them with the parking demand based on the MOMRA rates, a manual used in Riyadh for parking regulations, which also included checking for pedestrian circulation and safety.

What keeps me motivated in my work is the use of PTV traffic software which is a very powerful tool to model and analyse every possible traffic situation for both macro and micro scale. The fact that all software is synchronised makes the work very efficient and flexible, especially when you work on a transport planning project, switching from strategic planning to vehicle and pedestrian simulation.”

Interventions and improvements based on data
The results showed that some road segments and intersections were operating at a low level of service. To improve this, I proposed to widen some slip ramps, where necessary, add new ones and also u-turns on some roads to improve the circulation and traffic distribution. I also suggested to optimise the signalized intersections with inefficient time intervals. To increase the throughput, some intersections needed to be upgraded to two- and three-level interchanges, others could be improved by adding channelized right turns. While short-term solutions are always applicable as a fast way to solve temporary congestion, my study results and suggested interventions are currently under review with the local authorities to align them with their vision and development plans for the city.

 

Visualising and communicating study results
The challenge that PTV software solves for me in this and many other projects, is to visualise results and analyses – for a convincing reporting, especially when using PTV Visum, where you can handle various scenarios with the Scenario Manager, check for the congestion causes using the Flow Bundle feature, check for intersection delays quickly using the junction editor window and many other functions. I also use PTV software to present my study results to clients, mostly rely on the microsimulation software, PTV Vissim. It allows me to model my network at a high level of detail and complexity reflecting the realistic traffic situations for both traffic and pedestrian movements and showing the integration between these two modes of transport based on the behaviour of each group.
I have so far used PTV Visum, PTV Vissim, PTV Viswalk and PTV Vistro. What I like about them is that they cover the entire range of transport planning, from strategic planning and traffic engineering to vehicle and pedestrian simulation. The different solutions help me a lot when conducting traffic studies, since they cover a wide range of use cases related to transportation masterplan, public transport, planning and operations analysis, construction and development of roads, analysis of traffic engineering applications, economic efficiency analysis and different simulations.
More about Ahmad:
With a master’s degree in engineering and seven years of experience in transport planning and traffic engineering, Ahmad works as a transport planner at Khatib & Alami CEC in Beirut, where he uses PTV software almost on a daily basis. He has several PTV training certifications and in 2018, Ahmad also attended the PTV trainer program in Karlsruhe and he is now an officially certified PTV Visum trainer.
Connect with Ahmad on LinkedIn.
Get to know the PTV Expert:
Sebastian Sielemann, Product Manager for PTV Visum at PTV Group
Ahmad’s project is a great example that shows how each software works as a highly specialised tool and is tailored exactly to our customers’ needs. They enable them to analyse their cases with a high level of detail. With PTV Visum you model the demand, PTV Vistro is your perfect tool for node design and to assess and visualise your more complex planning areas, there’s PTV Vissim and PTV Viswalk. Of course, you can transfer your data within our software suite for an efficient workflow.
Our LinkedIn User Forums for Vissim and Visum are a great place to get to know traffic modelling experts and practitioners from all over the world and to exchange knowledge. Looking forward to meeting you there!

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