What is an autonomous car?
An autonomous car (also known as a driverless car, self-driving car or  robotic car) is a car that is capable of sensing what is around it and navigating without a person driving.

How does it work?
Autonomous cars use a variety of techniques to detect their surroundings, such as radar, laser light, GPS, odometry and computer vision. They have advanced control systems that interpret sensory information to identify appropriate navigation paths, as well as obstacles and relevant signage.

The following 2 minute video shows some of the different cameras that a Tesla autonomous car uses to sense where the road is and all the different objects that it comes close to such as people and other cars.

Let's program our own autonomous car! First, create a new Scratch project and delete the cat sprite.

https://scratch.mit.edu

Scratch: How to create a new project

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Go to the Scratch website using the link below and click on the 'Create' link in the blue bar at the top.

By default, each new project starts with the cat sprite already added. To delete the cat click on the x in the blue circle beside the cat in the sprite list.

https://scratch.mit.edu

Included with this step is a car picture that we're going to upload into our Scratch project. First download the picture file onto your computer and then upload it into your project.

Scratch: How to upload a sprite

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You can upload images and sprite files into your project. To upload a sprite follow these steps:

1. First save the image or sprite file onto your computer. You do this by right clicking on the image or link and then selecting 'Save image/link as...'.
2. Choose a location on your computer such as your desktop and save the file.
3. In your Scratch project, put your mouse over the Choose a Sprite button.
4. Click on the 'Upload Sprite' button.
5. Go to the folder you saved your file.
6. Select the file and click 'Open'.

The new sprite will upload into your project and appear in the stage area.

As the car sprite is very large, we'll need to shrink it so that it has room to move around. We're going to shrink it to 10% of it's original size.

Add the following code to the car sprite:

when green flag clicked set size to (10) %

We're going to use the backdrop editor to draw a racing track. To open the backdrop editor do the following:

1. Click on the stage backdrop in the bottom right. A blue box should appear around it.
2. Click on the backdrops tab in the top left. You should now see the backdrop editor.

Next we're going to draw a race track. First we will draw a green box that covers the stage area and then we will draw a black track. Follow these steps:

1. Select the Rectangle tool ().
2. Choose a green colour from the Fill tool.
3. Draw a large box that covers the stage area.
4. Select the paint brush tool ().
5. Choose a black colour from the Fill tool.
6. Set the thickness of the paintbrush to be 90.
7. Draw a simple track (keep it simple for now, you can make more complicated tracks later!).

Use the undo button if you make any mistakes. Once you've drawn your track click on the 'Code' tab up the top right of your screen.