The Environmental and Economic Impact of Advanced Smart Roadway Lighting Controls

November 5, 2022

A qualitative and quantitative analysis of how using effective lighting design and advanced lighting solutions to reduce the energy costs and GHG footprint of lighting by a total of 25.5%

This paper is ideal for civic planners and lighting designers, policy makers, and anyone who is developing business cases for Smart Lighting projects. The authors have used a real-world street lighting environment of 3,768 street lights as the basis for many of their assumptions, and assess the benefits of both an LED retrofit as well as the introduction of advanced smart lighting controls. This approach provides an excellent comparison between the opportunities for savings between LED retrofit and Smart Lighting projects.

This study includes assessments based on:

  • Cost per KwH of electricity
  • GHG footprint consisting of individual CO, particulate matter, CO2, SO2, and NO2 footprints
  • A comparison of high pressure sodium to LED, LED + dimming, and LED + advanced lighting control

The study does not include the Operations & Management savings from advanced Smart Lighting solutions. Other studies have shown the O&M costs of street lighting estimated at 85% of the total cost of ownership of street lighting with only 15% in capital costs (‘Energy efficient street lighting’, European PPP Expertise Centre, European Investment Bank (EIB), Luxembourg, 2013).

Key Findings

  • The economic benefits of adaptive dimming (smart) street lighting controls were estimated to range from 39% – 49%
  • The highest contribution (41%) to GHG emissions reduction was generated by re-lamping, i.e. replacing HPS fixtures by LEDs
  • The next highest contribution to GHG reductions (14%) was introducing an advanced adaptive lighting control system based on traffic volumes
  • In third place for GHG reductions (8%) was effective photometric design for the scenarios and areas being illuminated – which require Smart Lighting control to implement and is complementary to traffic volume-based dimming
  • The value of GHG emission allowances corresponding to the reduced CO2 emission volume, reached 10% of equivalent energy savings. This rate yields the 9% reduction in the lighting retrofit business case payback period
  • Moreover, for investments financed in the ESCO (Energy Service Company) model, we show that a payback period can be shortened by 9% (or even more, taking into account the current trend of the EUA price) thanks to incomes achieved due to the reduced CO2 emission

Using the authors’ estimate of GHG emissions saved, equal to 10% of electricity savings, we can estimate the contribution of advanced lighting control and effective lighting as 3.5% additional to the 14% GHG savings from advanced lighting control and 8% GHG savings from effectively designed lighting scenarios to estimate the potential GHG emissions benefit of Smart Lighting solutions at 25.5% of current GHG levels.

For clarity, the authors define advanced lighting control as:

“In the simplest case, it relies on scheduling, where luminous fluxes change according to the predefined rules at fixed hours and do not depend on actual environment conditions such as traffic flow intensity, ambient light level or weather conditions. In the advanced scenarios, a lighting installation performance is adjusted dynamically on the basis of environment state’s changes reported by a telemetry layer (induction loops, weather and occupancy sensors, etc.).”

The authors also define effective design, or optimization of the installation as:

“The scope of this [optimization] process may vary depending on a particular case, from appropriate lamp dimming and changing the fixture mounting angles or arm lengths to displacement of selected poles.”

In the article, “The Business Case for Smart Lighting as the Smart City Network“, we apply the authors’ excellent work, along with other sources, and apply it to a real-world city roadway, energy, CO2 equivalents, and lighting inventory data model. In this model, we find that the diversity of roadway classifications, city size, and mixture of lighting assets has a significant influence on potential cost savings:

  • 60%+ reduction in electricity use and related greenhouse gas footprint
  • 30%+ reduction in operations and maintenance costs
  • 60%+ increase in lamp life
  • 80%+ reduction in cost of leveraging a Smart Lighting network for sensor deployment
  • 4-5 year project payback for Smart Lighting
  • 5-6 year project payback for a Smart Lighting-enabled Smart City sensor network
  • Smart Lighting alone can provide 50% of the benefits compared with LED retrofit projects
  • Smart Lighting + Smart City network can provide 350% of the benefits of an LED retrofit

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The Business Case for Smart Street Lighting as the Smart City Network

Owners and managers of street and area lighting need high quality, reliable information to support informed decisions about Smart Lighting and Smart City-related projects. Until now, most of this information has either been scattered across a vast number of academic studies, or websites with unsourced information and marketing-speak.

This article is intended to provide a supportable, accurate framework to help answer these questions:  “Why should our organization care about Smart Street Lighting? What do street lights have to do with our Smart City vision? “

Factors Affecting Perceived Safety in Railway Stations

Feeling safe in public transport is essential for mobility, and fear of crime can be a larger problem for the individual than crime itself.

Among the most important characteristics affecting passengers’ safety are lighting, surveillance, other persons’ behaviour, time of day, and one’s own gender.

Creating safe spaces for railway and public transit facilitates increased use, which has follow-on socio-economic benefits for cities.

Designing and Implementing Advanced and Efficient Roadway Lighting

This 2016 paper by Adam Sedziwy and Leszek Kotulski is an essential for street lighting designers and engineers. The authors propose methodologies that drive savings by LED retrofit projects, advanced (aka Smart) lighting control and design, and operational & management cost savings available from advanced networked lighting systems.

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A bar chart describing the difference in the 10 year cost of operating sensors with and without a Smart Lighting-enabled Smart City network.

Tondo Smart Lighting also creates an open standards-based Smart City network for connecting sensors and other wireless and wired devices to Tondo's Cloud-IQ management platform.

This can reduce sensor and device deployment costs by 80% or more versus proprietary networks or individual cellular connections, with a 2.7x or greater benefit versus your LED retrofit project, and 3.5x over Smart Lighting alone.

A stacked bar chart that details the operating costs of street and area lighting, and the savings available with Smart Street and Area Lighting controls.

Read more about the Business Case for Smart Lighting on this link.

Normally open(NO) and Normally closed (NC) are terms used to define the states that switches, sensors or relay contacts are under when they are not activated.

A NO contact or a normally open contact is the one that remains open until a certain condition is satisfied such as a button being pressed or some other manner of activation such as those based on temperature, pressure, etc.

A NC contact or normally closed contact is the exact opposite of NO contact by function. It remains closed until a certain condition is satisfied.

Lighting control cabinets typically control a group of street lights or advertising signage from a "control cabinet". These controls have historically provided on-off functionality based on the time of day using an "astronomical clock"-based switch or daylight photosensor. Lights are controlled in groups with no individual control over a specific light.

Although new controllers such as Tondo's Edge-IQ controller have replaced the cabinet-based approach with new technologies that include advanced dimming, remote cloud-control, and support for functionality including sensors and switches, there are many outdoor lights and signs that do not support on-lamp control. Tondo's Cabinet-IQ controller provides new advanced IoT technology support for existing cabinet-controlled lighting.

CAT-M/LTE-M and NB-IoT are similar but have differences that may make one suitable over another, or simply selected based on the support for one or the other that is available in your area.

NB-IoT uses a narrow bandwidth of 200 kHz, where CAT-M uses 1.4 MHz. The maximum data rate for NB-IoT is ~ 250 kb per second, with CAT-M1 reaching ~ 1 Mbps. CAT-M is marginally less energy efficient than NB-IoT. Although NB-IoT has a lower speed, both NB-IoT and CAT-M are suitable for sensor communications since sensors typically do not require much bandwidth.

Both NB-IoT and CAT-M1 are supported under the 5G technology specifications and therefore are ideal for selecting as a standard for sensor communications.


CAT-M wireless (aka LTE-M) is a low-power wide area network (LPWAN) cellular data transmission standard that operates over the data and physical layer. CAT-M was designed for IoT projects, with an average upload speed between 200 kbps and 400 kbps.

Eddystone is an open-source Bluetooth advertising protocol originally designed by Google. It can be used by mobile device applications to deliver improved proximity-based experiences that include applications such as Google Maps.

These packets can be discovered with any Bluetooth LE APIs such as Core Bluetooth on iOS, or android.bluetooth.le on Android. You can also use them with Google’s Nearby Messages API, which can be integrated into an iOS or Android app, and receive “messages” in those apps when a person enters or exits a range of beacons.

You can read more about it on github.com/google/eddystone.

Source: US Department of Energy 2015 U.S. Lighting Market Characterization, issued November 2018

Tondo's 2022 estimate was calculated for each lighting category by applying market growth factors for each lighting category between 2015 and 2021 based on U.S. Census data to the DOE dataset.

The original Excel data set can be downloaded here.

A RESTful API is an architectural style for an application program interface (API) that uses HTTP requests to access and use data.

The API spells out the proper way for a developer to write a program requesting services from an operating system or other application.

You can read more from the source of this definition at TechTarget here.

A DIN rail is a metal rail of a standard type widely used for mounting circuit breakers and industrial control equipment inside equipment racks.

IP stands for "ingress protection". For IP67, this means:

"6" describes protection of solid particles: No ingress of dust; complete protection against contact (dust-tight). A vacuum must be applied. Test duration of up to 8 hours based on airflow.

"7" describes the protection from water: Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 meter (3 ft 3 in) of submersion). Test duration: 30 minutes.

Modbus is a data communications protocol originally published in 1979. Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting and communicating with industrial electronic devices.

Read more about MODBUS here.

RS-485, also known as TIA-485(-A) or EIA-485, is a serial communications standard.

Electrical signalling is balanced, and multipoint systems are supported. Digital communications networks implementing the standard can be used effectively over long distances and in electrically noisy environments.

This table describes the differences between 3G, 4G, and 5G cellular communications standards.

4G devices will work on 4G LTE networks and the earlier cellular technologies, including 3G, EGPRS, and 2G.

Smart city sensors require very little bandwidth, and 3G EGPRS and 4G LTE can easily support the required data rates.

5G networks are relatively new, and most 5G deployments use a combination of 4G and 5G networks.


A diagram describing the DALI smart lighting control system

DALI-2 refers to the latest version of the DALI protocol. While DALI version 1 only included control gear, DALI-2 includes control devices such as application controllers and input devices (e.g. sensors), as well as bus power supplies.

Read more at the DALI Alliance website: Compare DALI v1 vs DALI v2

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Zhaga Book 18 describes a smart interface between outdoor luminaires and sensing/ communication nodes.

Zhaga Book 18 allows any certified node to operate with any certified luminaire. Certified luminaires and sensing / communication modules are available from multiple suppliers, establishing an ecosystem of compatible products.

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The NEMA ANSI C137.4-2021 builds on the NEMA C137.41 7-pin connector standard and the DALI communication protocol. It has additional characteristics and features that align very closely with the D4i family of specifications from the DALI Alliance.

D4i and ANSI C137.4-2021 specify the digital communication between luminaires and devices including sensors and network lighting controllers. The expanded ANSI C137.4-2021 now includes energy reporting data and diagnostics and maintenance data.

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The NEMA ANSI C137.10 standard specifies roadway and area lighting equipment connector compatibility. The 3-pin standard does not provide for dimming control, but provides for on/off operation. The later standard C137.41 adds dimming control (5- and 7-pin connectors) and sensor control (7-pin connectors). The newer C137.4-2021 standard provides enhanced functionality and compatibility with the DALI D4i lighting and sensor control standard.

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The NEMA ANSI C137.41 standard specifies covers roadway and area lighting equipment connection interoperability. The 7-pin receptacle provides for dimming control and sensor communications.

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The NEMA ANSI C137.41 5-pin connector variant adds support for dimming control, but does not include sensor communications support which is supported by the 7-pin connector.

DALI, or Digital Addressable Lighting Interface, is a dedicated protocol for digital lighting control that enables the easy installation of robust, scalable and flexible lighting networks.

Wiring is relatively simple; DALI power and data is carried by the same pair of wires, without the need for a separate bus cable.

Read more at the DALI Alliance website: Introduction to DALI

The TALQ Consortium has established a globally accepted standard for management software interfaces to configure, command, control and monitor heterogeneous outdoor device networks (ODN) including smart street lighting.

This way interoperability between Central Management Software (CMS) and Outdoor Device Networks (ODN, so called ‘gateways’) for smart city applications from different vendors is enabled, such that a single CMS can control different ODNs in different parts of a city or region.

Read more at the TALQ website

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D4i is the DALI standard for intelligent, IoT-ready luminaires.

By taking care of control and power requirements, D4i makes it much easier to mount sensors and communication devices on luminaires. In addition, intelligent D4i LED drivers inside the luminaire have the capability to store and report a wide range of luminaire, energy and diagnostics data in a standardized format.

Infographic of Bluetooth Technology Global Standards

Highly reliable hardware, firmware, and software components that perform specific, critical security functions. Because roots of trust are inherently trusted, they must be secure by design. Roots of trust provide a firm foundation from which to build security and trust.

Read more at the National Institute of Standards and Technology: Roots of Trust

The 0.1, 0.2, and 0.5 accuracy class electricity meters established within ANSI C12.20-2015 are accurate to within +/-0.1%, +/-0.2%, and +/-0.5% of true value at a full load.

Read more at the ANSI Blog: ANSI C12.20-2015 – Electricity Meters – 0.1, 0.2, and 0.5 Accuracy Classes.

Source: US Department of Energy 2015 U.S. Lighting Market Characterization, issued November 2018

The full Excel data set that accompanies this report can be downloaded here.

Tondo's controllers utilize a chipset containing the ARM Cryptocell 300 cryptographic accelerator chip with hardware-protected vault and Root of Trust security. Read more about the ARM 300 family here: ARM Cryptocell 300 Family Overview

The world would collectively achieve 10,546 TWh of energy savings by 2030 [with energy efficient lighting], a sum comparable to over 40% of the world electricity generation in 2011. Saving this amount of energy would prevent the emissions of 5,400 Mt CO2, a figure equivalent
to over 15% of the global emissions in 2011.

Source: United Nations Environment Programme (2014). Green Paper - Policy Options to Accelerate the Global Transition to Advanced Lighting.