A115 London


By building a custom SMS parking payments solution for the city of Sofia, Bulgaria, A115 helped the parking authority increase revenues for on-street parking payments by over 250%. The surprisingly easy to use system became a digital landmark that put Sofia on the global map for mobile and transport innovations.

How the capital of Bulgaria became the world leader in mobile parking payments

by Jordan Dimov and Erika Guarino

In 2006, "Parkings and Garages" — the municipality-owned company in charge of on-street parking in Sofia at the time — had a problem. Almost nobody was paying for on-street parking. It was not that people didn't want to pay — the problem was with the payment process itself. Paying for on-street parking in Sofia at the time, as in many cities today, was a complex and frustrating experience.

A year later, with custom software built by A115, the city introduced one of the world's first SMS parking payment solutions. Today, after processing nearly 300 million payments, the system has helped the Sofia parking authority (now called "Sofia Urban Mobility Center") increase revenues by over 250%. Hundreds of thousands of SMS parking payments are processed every working day. More importantly. people love it.

The unique simplicity of the new parking payment process has become somewhat of a city symbol among its people and foreign visitors. Next time you you're in Sofia, try asking a local driver about it - chances are, they will be thrilled to show you how it works!

Sofia's parking conundrum

The capital city of Bulgaria is an economic, political and cultural centre. In 2015, Sofia generated 39% of the country's GDP and was ranked among the top 100 cities for outsourcing in 2016. With high labour productivity, a relatively high employment rate and growing urban migration, household income in Sofia is, on average, 52% higher than the rest of the country.

It is, therefore, not surprising that private car ownership in this old city has been growing rapidly since the 1990s. In fact, in 2009 the city was ranked number four for highest number of vehicles per capita in all of the EU, with over 560 cars for every 1000 inhabitants.

While this kind of growth in vehicle ownership, by its nature, reflects growth in the economic prosperity of a city, it also leads to inevitable parking issues. At the time, as it was then common in many cities, Sofia parking authorities relied on a paper-based system to regulate street parking. While theoretically useful, the "solution" was under-performing in practice - to say the least.

For years, any well-intending driver wishing to pay for their parking time, who was unfortunate enough to not have stocked on the required paper "vouchers" was forced to wait and fish around for a green-vest parking warden who could sell them one. The driver then had to carefully mark the date, time and location of their parked vehicle, before displaying the prized voucher on the front windscreen.

In addition to being cumbersome and inconvenient for drivers, this old-school system also made it difficult for the city to collect and track revenue and was largely ineffective in analysing actual parking patterns for long-term urban planning.

Understandably, citizens and the parking authorities became increasingly dissatisfied with this state of affairs. After long and careful consideration of alternative solutions, mostly involving meetings with foreign manufacturers trying to sell expensive, high-maintenance parking machines, the "Parkings and Garages" management team, supported by the then-mayor Boyko Borisov, made a decision. In a country with a deeply rooted Do-It-Yourself culture, the city was to build its own parking payments solution - and keep expenses to a minimum.

Unlike most other such undertakings, this one turned out to be a tremendous success.

The beauty of keeping things simple

The challenge was on. How do you build, from scratch, a reliable, cost-effective, long-term parking payments solution that the market could easily adopt, while addressing the control and revenue issues the parking authority had been facing?

Around that time, Premium SMS payments had been gaining popularity across the country. People were using texting as a convenient payment method for digital goods (music, on-line game assets), to support charities or to vote for their favourites on reality TV shows. The way it works is you send a text message to an advertised short-code (4-digit phone number) and the mobile carrier charges you at a pre-defined tariff (say, €1). At the end of the month, you pay your phone bill as normal, with all the Premium SMS services included as line-items. The mobile carrier then forwards the collected funds (minus commission) to the original service providers.

Due to its simplicity and popularity, the same Premium SMS model had been proposed for parking payments and everyone agreed it's worth a try.

Following several intensive weeks of meetings, workshops and discussions with decision-makers, parking consultants, the country's 3 mobile carriers, third party SMS payment gateways, lawyers, journalists and PR people, the project was officially announced as "in the works". A115 software engineers had already started building a prototype which, if successful, would have to quickly grow up to reliably support large amounts of daily transactions. It was in the news, the mayor was behind it, failure was not an option.

A bespoke solution built with open-source tools

The limited budget meant that commercial solutions or components with expensive software licenses were out of the question.

The natural choice was to build the custom solution with open-source tools and components. A115 chose the Python programming language, the Django web framework (for data administration, reporting and exposing an internal API) and the PostgreSQL database management system, famed for its industry-grade speed and reliability. The solution was built to run on servers powered by the Linux operating system.

Paying for parking would be reduced to taking the following simple steps:

  1. Find a space to park;
  2. Send a text message containing your registration plate number to the advertised short code number;
  3. Wait for the confirmation message, which doubles as a receipt;
  4. Get on with your regular schedule. You have successfully paid for 1 hour of parking time. The charge has been debited to your phone bill.

This process was designed to be straightforward even for the least tech savvy drivers. The solution does not require cash, credit or debit cards, smart phone, mobile data, or any form of registration in advance. Anyone with any mobile phone can pay in seconds, even if this is their first time parking in the city. As a further benefit, the driver would receive a reminder text message 15 minutes before their paid time expires, so they can decide if they want to extend their time by sending another SMS.

On the control-side, the parking wardens, equipped with mobile PDA devices would enter a vehicle's registration plate number to check whether parking was paid and at what time payment expires. They would also be able to provide additional information for each vehicle back to the system and issue parking violation tickets when required.

From pilot project to textbook example

After several internal iterations and multiple tweaks, the solution was first trialled as a pilot project on two streets in central Sofia, with a limited number of users. Satisfied with the trials, the parking authority officially announced the availability of the solution covering the entire "Blue Zone" of Sofia - a central area that includes more than 15 000 parking spaces and 90 streets. In 2012, a lower rate, wider "Green Zone" was included in the SMS parking solution, to practically cover the entire city.

In addition to seeing a drastic improvement in revenue and driver compliance, the "Sofia Urban Mobility Center" continues to benefit from access to real-time information on parking space utilisation, violations, disputes, revenues and insights into driver behaviour and parking patterns. Information, which has been vital to making well-informed decisions in planning the city's parking and transportation.

In the years since the city of Sofia and A115 first implemented SMS parking payments, the model has been adopted in every other major city in the country and has inspired dozens of similar projects around the world. The original solution has been featured in an EU-funded "Handbook of ICT solutions for improving co-modality in passenger transport", by Edinbourgh Napier University, as an example of a financially sensible technology with high impact factor for public transportation.

Parking management, of course, continues to be a recurring challenge for highly urbanised cities and their residents. In the UK, the BPA (British Parking Association) notes that drivers spend on average of 5.9 minutes looking for on-street parking space. Around 44% of the polled drivers called it (with typical British politeness) a "stressful experience".

While the lack or inaccessibility of physical parking space requires a different kind of transport solution, or perhaps a paradigm shift, innovative and collaborative mobile technologies empower local governments and vehicle owners to take matters in their own hands, by creating simple solutions that truly make a tangible difference.

Want to know more?

Contact us to find out how we could work together in your city:


Related resources