Speed Analysis in curved alignments of Highways

Velocidad Específica en Alineaciones Curvas

Specific Speed in curved alignments

Geometric design of highways is conditioned by many factors such as topography, geology and hydrology of the land, environment or social and urban factors. The most important is the project speed, which will condition the maximum speed at which you can travel with safety and comfort.

The road curves are circular alignments in plant. Furthermore, it gives transverse slope to compensate the centrifugal force (which would make the vehicle left the roadway) with the weight force on the ground of the curve. If you have the same slope in a curve, radius greater means higher flow rates. This speed is called specific speed.

RoadSpeedInspector application developed for Android mobile devices identifies the radius of curvature, analyzes and studies its relationship with the speed, to check the adequacy of the existing speed limit signs.

The application integrates a calculation engine. Radius of curvature are calculated based on the reference points (geographical coordinates) entered by the user with screen capture or GPS. As a result the calculated radius of curvature are represented on a map (straight or curved alignments). This information also allows determining for each curved alignment specific speed (according to spanish national regulation 3.1.IC), compensated centrifugal acceleration and coefficient of friction mobilized.

Who must download the application?

This new application is recommended for anyone who wants to know about sun glare when we are driving and especially it is directed to:

- Road Technical designers (engineers)

- Managers of road infrastructures

- Road Safety Auditors

Program Installation

The application uses Google Maps. You can download from official web Google Play Store.

RoadSpeedInspector App. can be requested free of charge filling out this form.


Play Store App

Play Store App

APP Description

You must install the application. Then you will see a new icon in the smartphone screen.  You must touch this icon and then the application begins.

Menu Inicio App

App Start Menu

You can choose three options: Captura desde GPS (record GPS coordinates), Captura desde mapa (record Maps coordinates) and Manual de uso (User’s Manual).

Pantalla GPS

Record GPS Coordinates

With the option “Captura desde GPS” you can record the road GPS coordinates using your smartphone.

Select ‘Activar’ button to start recording and ‘Desactivar’ button to finish. With ‘Escribir Datos’ button the information is saved in the disk (path/RoadSpeedInspector).  With ‘Cargar datos’ button you can see the GPS points had been registered in a map (geographycal coordinates).

Menu Inicio App

GPS Alignment

Recording Map Coordinate

With “Captura desde mapa” button you can record map coordinate. In order to get the point you must clicking in the map.

Ejemplo en Rotonda

Motorway junction Example

Simply swipe down the screen with two fingers and slide them. You can change the angle of visualization of the map.

Clicking on “Procesar Radios de Curvatura” button, (Radius of Curvature Process) curved alignments are estimated with radius of curvature (m), points that compose (initial and final) and error adjustment.

Procesado Radios Curvatura

Radius of Curvature Process

 Alineaciones Curvas Ajustadas

Curved Alignments Estimated


All the application options are in the Menu.

 Alineaciones Curvas Ajustadas


Tipo de Vista (View)

You can choose: Normal (normal), Híbrida (hybrid), Satélite (satellite) y Terreno (Maps).

- Mostrar Coordenadas y Distancia entre Puntos (Show Coordinates and Distance between points)

You can see the geographic coordinates ( Latitude and Longitude) in each point or the distance between two consecutive points.

Velocidad Específica (Specific speed)

Once radius of curvature are estimated, the application is able to calculate the specific speeds, so it is necessary to introduce the transverse slope (%) for each curve alignment. In a theoretical analysis, this transverse slope cant as shown in the Spanish national regulation 3.1.IC (depending of radius of the curve).

 Cálculo Velocidad Específica

Specific Speed Calculation

The results offered by the application, for each curve alignment are: the specific speed (km / h), the centrifugal acceleration (m / s2), the coefficient of friction mobilized and a graph of specific speed versus transverse slope used.

- Configurar tolerancia (Set Tolerance)

This changes the tolerance (%) with which you want to calculate the radius of curvature. A higher value of this parameter means that curve alignment contain more points (error adjustment may increase). By default, it is 5%.

- Exportar Ruta / Importar Ruta (Export/Import)

The application allows to save the road registered for his later use. You must select ‘Exportar’ button to save it and ‘Importar’ button to read the information again.

- Capturar Pantalla (Screen Capture)

You can do Screen Captures of anyone of the options that the application allows. The images will be saved in the folder ‘RoadSpeedInspector/Capture’. You can save the graphs in the folder RoadSpeedInspector/Graficas’.

- Mostrar/Ocultar Puntos (Show / Hide Points)

You can hide the points to see the risk map better.

Move a Point

You can Press to select a point and then slide your finger to move it.


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