What is Traffic Engineering Design?

To understand a traffic engineering design, you first need to understand what a traffic engineer is. Simply put, a traffic engineer is a qualified engineer who studies, analyzes, and develops road projects.

Traffic engineering design is the final of those three options – developing. It is a traffic engineer’s job when designing to create a transportation system that is safe and efficient. Taking a variety of factors into consideration – such as needed intersections, surrounding buildings, and the volume of traffic in the area – a traffic engineer will design a transportation system that is both efficient and safe.


Key Elements of Traffic Engineering Design


Traffic Flow

When a traffic engineer is designing a transportation system, they need to understand the volume of traffic in the area and consider how their new or improved roadways will handle it. Parts of the design like signs, signals, extra lanes, and speed limits will all impact traffic flow. The goal is to keep traffic flowing efficiently and safely and to avoid congestion.


Safety is the number one concern for traffic engineers. They work diligently to understand the needs of the area they’re designing to ensure that everything is built to optimize safety for pedestrians as well as drivers. They will add proper signs, signals, and extra lanes to ensure traffic is controlled and safe as it moves through the area. 


When designing a new transportation system, a traffic engineer’s second concern is efficiency. They’ll either collect their own data or use data from a traffic study of the area to determine traffic volumes and behavior at different times of day, as well as the causes of certain traffic behavior like delays. With a combination of roadway design, speed limits, lane additions, and safe intersections, a traffic engineer can create an efficient system that reduces travel time for all drivers through the area. 


With efficiency as a traffic engineer’s second priority, it makes perfect sense that sustainability and traffic design can easily work together. By reducing travel times and keeping traffic flowing, a vehicle’s emissions will be lowered when using a well-designed system.


Traffic Engineering Design Process

A traffic engineer’s design process will first begin with collecting or analyzing previously collected traffic data on the area they’re designing for. Using this information, they will then begin to determine what needs to be included in their traffic system. Usually, the first thing to be decided is the number of standard driving lanes that will be included. This is determined using a ratio of traffic volume to capacity. They will then decide if any auxiliary lanes will be needed, such as left or right turning lanes. This is determined using the amount of visibility and traffic flow through the intersection in question. 

The intersection will also need to be designed, and the traffic engineer choosing whether the intersection will be controlled through 2 or 4-way stops, traffic signals, or a roundabout. It is at this time that the engineer will also decide how the auxiliary lanes – if there are any – will be controlled. Finally, pedestrian traffic will be considered, and the engineer will determine if walkways and walking signals need to be added.

After everything has been decided, the traffic engineer will need to put all of the pieces together and evaluate the system as a whole to ensure it runs safely and efficiently. 

Pre-Design Considerations


Site Analysis

Before creating a design, traffic engineers need to conduct a site analysis to determine what needs the site may have for the area’s traffic. They will need to take note of the surrounding area – businesses, schools, railways, protected lands, etc. – and investigate any local policies that might affect their work. 

Traffic Surveys

A traffic survey is a survey conducted by traffic engineers to determine how traffic moves through a particular area. These usually take 2-4 days per intersection to complete and need to occur throughout the day to ensure both peak and non-peak hours are factored in. One of the most popular ways a traffic survey is conducted is with the use of rubber hoses. These hoses run across the road and connect to a meter that counts each vehicle that passes while also determining what type of vehicle it is. These hoses also collect data on what speed the vehicle is going when it passes over the hose. 

Traffic engineers will also need to count the turning movements and pedestrian movements in the area. This is usually done in person, but some engineers deploy video technology to try and capture the information needed. The number of vehicles, the type of vehicles, and how the vehicles are moving through the intersection all need to be recorded. 

Public Consultation

As a transportation system is built for the public, it only makes sense that the public is considered when a design for a new or improved system is being created. Traffic engineers often work with the public, whether it be through in-person meetings or online surveys, to determine how the public feels about the process.

When creating a design, there are several factors that a traffic engineer needs to consider. 

Road Geometry

Road geometry is a major consideration, with decisions being made regarding the lengths and widths of lanes as well as median dimensions and the radius allotted for turns. The biggest thing this will depend on is the type of vehicles that frequently traffic the area. Larger vehicles lead to larger lanes and turns. 

Traffic Control Devices

Traffic engineers will also need to consider what traffic control devices will be used in the intersections. These include traffic lights, road signs, and road markings. 

Pedestrian Facilities

If there is a high volume of pedestrian traffic through the system, the traffic engineer will need to create pedestrian walkways and decide on if there will be light signals for those walkways. 

Bicycle Facilities

Using data collected about the area, traffic engineers will need to decide if bicycle lanes will need to be included in their design. If a school or university is nearby, this is likely to be the case. Many popular areas within cities also tend to need bicycle lanes as many people choose to travel via bicycle over navigating vehicle traffic. 

Transit Facilities

Any nearby transit facilities will need to be factored into the system design. Things like parking lots, loading zones, bus stops, and railways will all impact how traffic flows through the area. If these things are ignored, the design will lack allowances for these issues and fail. 


Landscaping may not seem like the most important thing to consider when a traffic engineer is creating a design, but it’s still a factor. This is especially true when the engineer is designing for a residential area or an area with a lot of businesses. Aesthetics are important to many people. Some cities may even have policies regarding landscaping and road projects. 


Traffic engineers will have to decide the lighting needs of the system they create. Taking into account the surrounding area, they may decide to include additional lighting fixtures within their design. For example, if their road project is in an area with very few buildings or other sources of lighting, they may choose to include street lamps along the road to increase the safety of those driving through the system at night. 

Signage and Markings

This is one of the more important factors that will need to be considered by a traffic engineer. They’ll need to decide how they will stripe the roads, what markings they will add to the roads, and what signs will be used. This includes exit signs, speed limit signs, and yield or stop signs. 


It’s important for traffic engineers to keep in mind the drainage of the area they’re designing for. They want to avoid building roadways that will easily flood.  

Traffic Engineering Design Execution


1. Construction Phase

When building or improving a traffic system, the traffic engineer needs to consider the construction phase carefully. Most want to avoid detours, using different techniques to control traffic through the area as work is conducted. If they find a detour is necessary, they’ll need to study the area to find the best options for a route. They’ll need to create a timeline for the project’s construction and ensure the timeline is adhered to while also keeping workers and drivers in the area safe. They’ll need to decide what lanes will be closed and when, as well as the speed limits while workers are present.

2. Implementation Phase

With construction underway, the implementation phase begins. Traffic engineers will need to oversee construction every step of the way and help handle any issues that arise. The engineers will work closely with the people they’ve commissioned to ensure all goes smoothly and will make adjustments to their design if it’s deemed necessary. They’ll also make sure the steps they put in place to control traffic are working effectively. 


Traffic Engineering Design Evaluation

After a new traffic system has been created, the system needs to be evaluated. Traffic engineers need to continue to monitor the area, collecting and analyzing new data to ensure that traffic is flowing efficiently and safely through the system. They’ll also welcome feedback from the public and be willing to tweak their design to improve it if necessary. 



Traffic engineers are experts who can study and analyze traffic, as well as create designs to change traffic flow and patterns. Some things a traffic engineer may work to create are roadways, intersections, bicycle lanes, and pedestrian walkways. Their main goals when designing are safety and efficiency. From the initial stages of planning to the implementation and evaluation of a new road system, traffic engineers oversee every step of the process to ensure these goals are met.