How Is a New Road Constructed?

Roads and road markings are what make traffic possible. But how is a road typically constructed? What are the necessary steps and materials required to build a road that will last for decades and ensure safe use throughout its lifespan? This article will look at the general way of constructing roads and, no less important, how to mark them correctly in order to obtain the best results for the road users.

Design

Many factors come into play when designing and constructing a new road. The environment and sub-grade, water interception, sound emission, appropriate materials and construction design are all part of the planning phase. Engineers will usually evaluate all these parameters and design a construction plan that the project contractor will implement.

Earthworks

Earthworks involves the removal and/or adaptation of top-soil in order to prepare the land for the new road. The aim is to ensure that the surface is ideally prepared for paving and that the soil is ideal for load distribution of the traffic. Excavators, dump trucks and rollers are employed to remove and/or re-arrange soil, gravel and sand.

Paving and Quality Control

Several options for pavement layers exist, depending on the requirements, location and nature of the new road. Flexible pavement and rigid pavement methods are most commonly used. The flexible pavement uses a bitumen top-coating and relies on grain-to-grain load distribution while the rigid pavement uses a concrete surface and distributes traffic loads using concrete slabs underneath. The image below shows the most important layers used in road construction, regardless of the method used.

Road Construction and Road Marking - Construction Layers

Between layers, different coatings are used to bind the layers together and to shield underlaying layers from excess amounts of water. Seal coat, tack coat and prime coat are all applications used for these purposes.

The quality of each layer needs to be assessed before the next layer or coating can be applied. Density, stiffness, uniformity, vibration frequencies etc. are all part of this quality control. As-built surveying is used to verify the height of the different layers to ensure the correct geometry of the road layers throughout the construction process. This is described in more detail below.

Road construction and road marking

Materials

Different materials are used for different road projects but the most common materials are gravel, cement concrete, bitumen or black top as well as stabilized soil. The different types of coat between pavement layers also consist of concrete and bitumen materials.

Marking

Last but not least, road markings are used to ensure a safe flow of traffic on the new road. There are many different types of road markings which depend on local or regional traffic regulations. Longitudinal road markings, intersectional markings, markings for parking and objects etc. are all used to instruct drivers on the road. Road lines are usually set out or pre-marked by land surveyors before any permanent road line painting is applied in order to ensure the correct position, direction and length of the lines.

Road pre-marking for road construction and road line painting

What Different Types of Road Markings Are Used?

A variety of lines are used to make traffic safe and efficient. Solid lines, dashed lines, wide lines, double lines, multiple color lines and diagonal lines are some of the types of road markings used. Numbers, letters and symbols/icons may also be used to instruct drivers. The use of lines and symbols as well as the interpretation by drivers and users of course depend on the regulations in that country or region.

Road markings are an essential part of ensuring a new road to protect and guide drivers. However, signs and signals are also employed to make sure that instructions are as clear and concise as possible.

How Is the Road Line Painting Applied?

The road line painting which typically consists of thermoplastic resin is applied using specialized road marking vehicles. These vehicles distribute the paint at the right amount and at the right pace in order to ensure that the lines have the correct length and thickness. Road marking vehicles may have an internal heater to heat up the thermoplastic paint which is a solid powder at room temperature. The plastic may also be heated externally and then loaded onto the vehicle which will keep the plastic in a fluent state until applied to the road.

Even though a computer is often used to ensure a correct distribution of the paint, the manual control of the marking vehicle still requires a lot of skill and expertise on the part of the steersman. Once applied, the thermoplastic is very hard to alter or erase. The paint is very durable as it must be able to withstand many years of changing weather conditions as well as the tear from vehicles on the road.

Other types of road line paint include cold plastic paint and two-component paint. However, thermoplastic paint is most commonly used due to its durability.

Road marking robot for pre-marking new roads

What Road Marking Equipment Is Needed?

The road marking process can be divided into two types of marking; pre-marking and permanent marking. The permanent markings, using resilient materials such as thermoplastic resin, need to be 100% accurate when applied. Otherwise, removing and re-arranging painted lines will drive up costs and project execution time. This is why pre-marking is necessary.

The pre-marking process has been a manual process for a long time, requiring land surveying skills to stake out the lines using GPS rods and/or total stations. For a new highway section, many lines need to be accurately marked down to a few centimeters’ precision and sometimes even below that. A new stretch of highway including several lanes and different line types can easily take several days to set out, often leading to mental and physical fatigue for surveyors.

Once the road marking positions have been staked out by surveyors, road marking crews often need to extend the lines using strings, tape measures and spray cans so that it is absolutely clear where the permanent markings are to be painted.

Positioning and painting the pre-marked lines can also be done automatically, using a road marking robot for pre-marking. The design of the road markings (position, line type, line length, intervals etc.) is typically already determined in the design phase and is available as two- or three-dimensional data. This is very often a DWG file which contains all the necessary information to place the lines. The robot is able to use this data and mark out the lines using the attached spray can.

Road construction and road marking

Efficiency and Safety in Road Construction

In order to ensure high precision and accuracy, the robot uses GPS satellite signals as well as RTK correction signals to pre-mark the lines down to centimeter accuracy. The robot can also be used with a total station for even greater accuracy. Automating the pre-marking phase can save road marking companies and land surveyors a lot of critical time and allow them to complete more work faster and in a more efficient way. Furthermore, land surveyors who need to survey the different road layers during construction can also use the robot for high-precision as-built surveys using a total station.

The road marking robot can work un-aided for 8 hours, completing up to 30 km (18.6 mi) miles in one shift. One of our road marking customer cases evaluated the speed of the robot compared to that of a road marking crew. Pre-marking 1 km (0.6 mi) took 6 man hours for the crew and only 17 minutes for the robot. This is both due to the speed and accuracy of the robot as well as the fact that locating the position of the lines AND marking out the lines is all done in one step when using a robot. This naturally leads to high efficiency gains for road marking companies who can complete the pre-marking phase much faster and allow the permanent marking to begin.

In addition, refurbishments and maintenance work on existing roads with live traffic can be a dangerous place to work for road marking crews and surveyors. Using a robot allows human personnel to be removed from hazardous work places and to control the robot from a safe distance.

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