Transport Accident Commission

The Google Lighthouse performance score is a metric that measures the speed and performance of a website. It’s an overall score that ranges from 0 to 100 and is generated based on a number of different performance metrics, such as the time it takes for a website to load, the time it takes for a website to become interactive, the size of the resources used by the website, and other factors that impact the user experience.

A high performance score in Google Lighthouse indicates that a website is fast and responsive, which can lead to a better user experience and improved search engine rankings. On the other hand, a low performance score can indicate that a website is slow and unresponsive, and can negatively impact the user experience.

Core Web Vitals are a set of specific factors that Google considers important in a webpage’s overall user experience. Core Web Vitals are made up of three specific page speed and user interaction measurements: Largest Contentful Paint, First Input Delay, and Cumulative Layout Shift.

All the tracking scripts on the site generated ~318 KB of data

A tracking script is a code snippet designed to track the flow of visitors who visit a website. Media, advertising, and analytics organisations will provide a script to add to your website that sends data directly to their servers. This data can then be used to measure goals and conversions, analyse user behaviour, and influence advertising campaigns.

Consider how much of this data you actually need and use? How often do you review the analytics data, and does this inform genuine change? Are you actively running social media campaigns? Consider pausing or removing tracking scripts that aren’t being actively used.

By optimising the following images, roughly 2 MB could be removed from the transfer size, about 41%. This would reduce the CO2 generated per page load from 1.45g grams to 0.86 grams.

Images should be optimised for the web for several reasons:

1. Reduced file size: Optimizing images can result in a smaller file size, which can help to reduce the amount of data that needs to be downloaded. This can lead to faster page load times and improved performance.
2. Improved user experience: Optimising images can help to improve the overall user experience, as pages with optimised images load faster and are more responsive.
3. Lower emissions: Optimising images can help to reduce the emissions associated with data transfer, as less data needs to be transmitted over the network.
4. Better accessibility: Optimising images can make them more accessible to users with slower connections or limited data plans.

Fonts should be subsetted to reduce the file size, improve performance, and reduce emissions. Subsetting a font involves removing any characters that are not needed for a particular use case, resulting in a smaller file size and faster page load times. Some specific reasons why fonts should be subsetted include:

1. Reduced file size: Subsetting a font removes any unused characters, which can result in a smaller file size. This can help to reduce the amount of data that needs to be downloaded, leading to faster page load times and lower emissions.
2. Improved performance: Fonts that are subsetted are faster to load and render than fonts that are not subsetted. This can help to improve the overall performance of a website, leading to a better user experience.

Overall, subsetting fonts is a good practice for anyone looking to optimize the performance and reduce the emissions of a website of a website.

WOFF2 is considered to be the best font format for web use because it provides a good balance of file size and compatibility. Some specific reasons why WOFF2 is a good font format include:

1. Small file size: WOFF2 is a compressed font format, which means that it has a smaller file size compared to other font formats like TTF or OTF. This is important for web use because smaller file sizes can help to reduce the amount of data that needs to be downloaded, leading to faster page load times.
2. High-quality font rendering: WOFF2 provides high-quality font rendering, making it a good choice for use on the web.

It’s worth noting that WOFF2 is not the only font format that can be used on the web, and there may be cases where other formats like WOFF or TTF are more suitable, depending on the specific requirements of the website. However, for most cases, WOFF2 is considered to be the best font format for web use due to its combination of small file size, good browser support, and high-quality font rendering.

First Contentful Paint (FCP) is a performance metric that measures the time it takes for the first piece of content to be rendered on the screen when a user navigates to a web page. This content can be any visual element on the page, such as text, images, or a background color.

FCP is important because it directly affects the perceived speed of a website, and can impact user engagement and conversion rates. A faster FCP can lead to a better user experience and improved performance.

Here are a few ways you can optimise your FCP:

1. Optimise images: Large, unoptimised images can slow down a page’s FCP. You can optimise images by compressing them, reducing their dimensions, and choosing the right format for each image.
2. Minimise HTTP requests: Each resource requested by a web page, such as images, scripts, and stylesheets, requires a separate HTTP request. Minimising the number of HTTP requests can help to reduce the time it takes for a page to render.
3. Prioritize critical content: Prioritizing critical content, such as above-the-fold content, can help to ensure that users see something on the screen quickly, even if the rest of the page is still loading.
4. Reduce server response time: A slow server response time can significantly impact FCP. Optimizing server-side code and server settings can help to reduce response times and improve FCP.
5. Use a performance monitoring tool: There are many tools available that can help you monitor your website’s performance, including FCP. These tools can help you identify performance issues and track your progress as you implement optimizations.

The carbon footprint of a website can be calculated by estimating the amount of energy consumed by the data center hosting the website, as well as the energy consumed by users accessing the site. Factors that can influence a website’s carbon footprint include the size of the site, the amount of traffic it receives, and the technology and hosting infrastructure used to host the site.

All the tracking scripts on the site generated ~318 KB of data

A tracking script is a code snippet designed to track the flow of visitors who visit a website. Media, advertising, and analytics organisations will provide a script to add to your website that sends data directly to their servers. This data can then be used to measure goals and conversions, analyse user behaviour, and influence advertising campaigns.

Consider how much of this data you actually need and use? How often do you review the analytics data, and does this inform genuine change? Are you actively running social media campaigns? Consider pausing or removing tracking scripts that aren’t being actively used.

By optimising the following images, roughly 2 MB could be removed from the transfer size, about 41%. This would reduce the CO2 generated per page load from 1.45g grams to 0.86 grams.

Images should be optimised for the web for several reasons:

1. Reduced file size: Optimizing images can result in a smaller file size, which can help to reduce the amount of data that needs to be downloaded. This can lead to faster page load times and improved performance.
2. Improved user experience: Optimising images can help to improve the overall user experience, as pages with optimised images load faster and are more responsive.
3. Lower emissions: Optimising images can help to reduce the emissions associated with data transfer, as less data needs to be transmitted over the network.
4. Better accessibility: Optimising images can make them more accessible to users with slower connections or limited data plans.

Fonts should be subsetted to reduce the file size, improve performance, and reduce emissions. Subsetting a font involves removing any characters that are not needed for a particular use case, resulting in a smaller file size and faster page load times. Some specific reasons why fonts should be subsetted include:

1. Reduced file size: Subsetting a font removes any unused characters, which can result in a smaller file size. This can help to reduce the amount of data that needs to be downloaded, leading to faster page load times and lower emissions.
2. Improved performance: Fonts that are subsetted are faster to load and render than fonts that are not subsetted. This can help to improve the overall performance of a website, leading to a better user experience.

Overall, subsetting fonts is a good practice for anyone looking to optimize the performance and reduce the emissions of a website of a website.

WOFF2 is considered to be the best font format for web use because it provides a good balance of file size and compatibility. Some specific reasons why WOFF2 is a good font format include:

1. Small file size: WOFF2 is a compressed font format, which means that it has a smaller file size compared to other font formats like TTF or OTF. This is important for web use because smaller file sizes can help to reduce the amount of data that needs to be downloaded, leading to faster page load times.
2. High-quality font rendering: WOFF2 provides high-quality font rendering, making it a good choice for use on the web.

It’s worth noting that WOFF2 is not the only font format that can be used on the web, and there may be cases where other formats like WOFF or TTF are more suitable, depending on the specific requirements of the website. However, for most cases, WOFF2 is considered to be the best font format for web use due to its combination of small file size, good browser support, and high-quality font rendering.

This page generated ~1.45grams of CO2

By moving to a host using renewable energy, this could be reduced to ~1.26grams of CO2.

Sustainable web hosting refers to hosting services that are designed to minimise their impact on the environment and to promote sustainability. This can include using renewable energy sources, reducing waste and emissions, and implementing best practices for energy efficiency.

Sustainable web hosting providers aim to reduce their carbon footprint by using energy-efficient server hardware, data centres, and networking equipment, as well as implementing environmentally friendly policies and practices. For example, some providers may use renewable energy sources, such as wind or solar power, to power their data centres, or they may use high-efficiency cooling systems to reduce energy consumption.

The accessibility score in Google Lighthouse is a metric that measures how well a website is designed for users with disabilities. The score ranges from 0 to 100, with higher scores indicating better accessibility.

Google Lighthouse evaluates a website’s accessibility based on a number of different factors, such as the presence of alternative text for images, the use of semantic HTML, the ability to navigate the page using only a keyboard, and the use of appropriate color contrasts.

A high accessibility score in Google Lighthouse indicates that a website is well-designed for users with disabilities and provides an inclusive user experience. On the other hand, a low accessibility score can indicate that a website has barriers that make it difficult or impossible for some users to access and use the content.

In automated testing, this page scored 80% for accessibility on desktop. Keep in mind that automated accessibility testing is not perfect and that manual tests, use case testing, or usability testing should be completed as well.

Google Lighthouse evaluates a website’s best practices based on a number of different factors, such as the use of HTTPS encryption, the use of efficient caching policies, the implementation of modern web technologies, and the avoidance of deprecated technologies.

A high best practices score in Google Lighthouse indicates that a website is well-designed and follows best practices for web development, which can lead to better performance, security, and accessibility. On the other hand, a low best practices score can indicate that a website has room for improvement in terms of following best practices.

Google Lighthouse evaluates a website’s SEO based on a number of different factors, such as the presence of title and description tags, the use of header tags, the presence of structured data, the use of image alt tags, and the use of crawlable links.

A high SEO score in Google Lighthouse indicates that a website is well-optimized for search engines, which can help to improve its visibility in search results and increase its organic traffic. On the other hand, a low SEO score can indicate that a website has room for improvement in terms of its optimization for search engines.

While a high SEO score can help to improve a website’s visibility in search results, it’s not a guarantee of higher rankings, as search engine algorithms take many other factors into account when determining the ranking of a website.

The Progressive Web App (PWA) score in Google Lighthouse is a metric that measures the quality of a website as a progressive web app. The score ranges from 0 to 100, with higher scores indicating better performance and functionality as a PWA.

A progressive web app is a type of web application that combines the best features of both web and native apps, providing users with a fast, reliable, and engaging experience on any device.

Google Lighthouse evaluates a website’s PWA performance based on several key factors, such as the availability of a service worker, the presence of a web app manifest, the ability to install the app on the home screen, and the performance of the app under poor network conditions.

All the tracking scripts on the site generated ~318 KB of data

A tracking script is a code snippet designed to track the flow of visitors who visit a website. Media, advertising, and analytics organisations will provide a script to add to your website that sends data directly to their servers. This data can then be used to measure goals and conversions, analyse user behaviour, and influence advertising campaigns.

Consider how much of this data you actually need and use? How often do you review the analytics data, and does this inform genuine change? Are you actively running social media campaigns? Consider pausing or removing tracking scripts that aren’t being actively used.

HTTP security headers are special HTTP headers that can be added to a website’s response to help improve its security. They are important because they can help to protect a website and its users from various security threats, such as cross-site scripting (XSS) attacks, cross-site request forgery (CSRF) attacks, and other types of malicious activity.

It’s important to note, however, that implementing HTTP security headers is just one aspect of a comprehensive security strategy, and that other measures, such as regular software updates, secure coding practices, and regular security audits, are also important for maintaining a secure website.

It's important to note, however, that implementing HTTP security headers is just one aspect of a comprehensive security strategy, and that other measures, such as regular software updates, secure coding practices, and regular security audits, are also important for maintaining a secure website.

Google Analytics collects data on website users and their behaviour, which can raise privacy concerns for some visitors. Website owners who use Google Analytics have access to a range of data points, including IP addresses, browser types, device information, and user behaviour on the site.

While Google Analytics does provide some tools to help website owners protect the privacy of their visitors, such as data retention controls and the ability to enable IP address anonymisation, it’s important for website owners to be transparent about the data they collect and how they use it. Website owners should also take steps to ensure that any third-party tools they use, including Google Analytics, comply with relevant privacy laws and regulations.

Additionally, some users may choose to block Google Analytics tracking using ad-blocking software or browser extensions that prevent tracking cookies from being set. This can impact the accuracy of website analytics, but website owners should respect the privacy preferences of their visitors and provide alternative means for users to access the site and its content.

The following alternatives to Google Analytics are privacy focussed, meaning they don’t compromise the visitors privacy for the sake of data collection and reporting.

• Plausible
• Cabin
• Fathom
• Simple Analytics
• Insights
• Matomo