14 minute read
IMPROVING THE ENVIRONMENTAL IMPACT OF CONSTRUCTION SITES
NICOLAS BLANDAMOUR LOCALSOLVER IS A FASTGROWING SOFTWARE COMPANY in optimisation and decision support. The team is developing LocalSolver Optimizer, an innovative optimisation solver. In addition to this flagship software, LocalSolver offers tailor-made optimisation solutions with ergonomic interfaces for various businesses. The company counts among its customers the most prominent companies worldwide, like Starbucks, Macy’s, Microsoft, Chewy, Roadie, Procter & Gamble, Air Liquide, Bosch, Publicis, JCDecaux, Airbus, Renault, Repsol, Fujitsu, Softbank, and Sony.
LOCALSOLVER’S INNOVATIVE APPROACH LocalSolver’s team develops a generalpurpose mathematical optimisation solver for operational researchers, data scientists, and software developers to quickly solve optimisation problems and, beyond, build and deploy optimisation applications effortlessly. One of LocalSolver
Optimizer’s strengths is its innovative modelling approach that makes the mathematical modelling of Vehicle Routing, Production Scheduling, Workforce Scheduling, and many more types of problems much simpler than traditional solvers. The resulting models are compact and natural while providing much better results, particularly for large instances in limited running times. LocalSolver’s team also offers reactive and dedicated support to the users of the optimiser. The team works closely with its users and helps them model and efficiently solve their optimisation problems until they are fully satisfied.
HESUS Recently, the French start-up, Hesus, was able to leverage the power of LocalSolver Optimizer. As a European leader in sustainable solutions for the management of construction site soil, the group is positioned in all strategic, operational, and logistical areas of expertise with proven expertise in polluted sites and soils. They assist all players in the construction and public works sector during the design, construction, and demolition of infrastructures and buildings. Present in six countries, they manage nearly 2 million tons of soil each year in France and Europe and recover an average of 82% of the spoil on its sites.
A CHALLENGING TRANSPORTATION PROBLEM Dozens of construction sites delegate their transportation logistics for excavated earth and construction materials daily to Hesus. Transport infrastructure or building sites require the movement of large quantities of excavated soils and building materials. The ground extracted from these construction sites can present different pollution levels, requiring specialised centre treatments. Once the treatment has been completed, the inert soil obtained can be reused as backfill for earthworks, while the extracted materials, such as gravel, can be used as raw material for other construction sites. The different trips needed to move these materials and the operational constraints lead to a difficult Vehicle Routing Problem (VRP). In addition to the traditional constraints of a VRP, it is necessary to take into account the road traffic, the opening hours of construction sites and treatment centres, and specific regulatory constraints such as the maximum driving time and break times to have the most realistic routes possible.
Mathematically speaking, this problem is related to a VRP with full truckloads. The main objective is to reduce as much as possible empty trips for dump trucks, or in other words, unproductive minutes and kilometres for the whole fleet of trucks.
More than 300 tours are requested per day for evacuations/deliveries. This represents 10,000 tons of material to be moved between construction sites and treatment centres.
HESUS DISPATCH SOLUTION The resulting optimisation solution based on LocalSolver as the core optimisation engine, called Hesus Dispatch, optimally matches possible drop-off locations with potential loading sites along the truck routes while respecting all their operational constraints. Thus, the application allows Hesus to reduce its transportation costs and carbon footprint of truck journeys by 10% to 15%.
The optimisation engine can identify how to efficiently mutualise a truck across several sites and treatment centres to reduce the length of empty transition
FIGURE 1 THE CIRCULAR ECONOMY
rides between valuable trips. For instance, it can lead a truck to evacuate excavated soils from a site to a treatment centre further than the nearest ones but close to another site with transportation needs. The extra distance travelled to reach this treatment centre will be more than compensated by the short deadhead ride to move to another site where the truck will be reloaded to continue its journey. Identification of efficient repositioning among the numerous possible combinations resulting from the size of the problem is one of the levers used by the optimisation to improve operational efficiency.
Another improvement comes from a better filling of trucks timetable, which reduces the number of trucks needed to perform the transportation. The engine will exploit differences in sites and centres’ opening hours to increase the used time range of the truck with respect to regulatory constraints. The effective time range of a truck can also be increased by tweaking the end of the truck roadmap to avoid returning too early to the truck depot. For example, at the end of a day, a truck may evacuate soils from a site to a nearer centre than the one used during the rest of the day. This nearby centre can be less attractive in terms of treatment costs than the others but allow an extra tour to be planned at the end of the day, a tour which is not possible for other treatment centres due to daily travel time limitation.
Finally, the optimisation engine chooses the most suitable contractors for truck providers and treatment centres regarding geographic implantation and prices. The tradeoff is indeed challenging to find for a planner at hand. Choosing the truck depots and processing centres closest to the sites reduces the distance travelled, but it increases the overall cost as those contractors close to sites are located in urban areas and thus generally expensive. On the contrary, choosing the cheapest contractors will increase the distance as they are located far from the sites, resulting in a higher number of trucks and an important transportation cost despite a reasonable unit price.
To ease the change management and the adoption of the decision-support tool by the logistic planners, Hesus Dispatch allows fine control of the complexity of the routes generated by the engine. Kevin Jahier, Logistics Director at Hesus: “The optimisation engine helps me every day to dispatch our customer orders. On top of saving me a lot of time that I can dedicate to other high-value-added tasks, it is really exciting to discover each day how the routes can be optimised and to contribute to bringing sustainable solutions for construction site soils.”
AN ENVIRONMENTAL IMPACT Because the excavated soil from one site can become a resource for another, Hesus, Greentech’s partner for construction sites, puts the circular economy, seen in Figure 1, at the heart of its solutions. They favour re-using soil and materials while ensuring soil compatibility and the absence of contamination risks. Hesus prioritise the re-use of soils, which allows controlling costs while acting to preserve resources and reduce CO2 emissions. Hesus partners with more than 900 sectors, including treatment and decontamination centres, quarries, and storage facilities. Thus, each site benefits from a service adapted to the type of pollution of its soils and waste. In 2020, Hesus achieved an average recovery rate on its sites of over 84%.
O.R. has proven to play a significant role in solving Hesus’ challenging transportation problem both from an operational and environmental point of view. That’s why the LocalSolver team is glad to help Hesus’ team achieve even more ambitious goals in the years to come.
Nicolas Blandamour is a Vehicle Routing Optimisation Expert at LocalSolver. He joined the company right after his graduation and has worked since as a member of the R&D team to improve the performance of LocalSolver Optimizer. Nicolas also developed several tailor-made vehicle routing applications in various business fields, among which Hesus Dispatch was selected as a finalist for the Indus’RO price given by the French O.R. society rewarding best O.R. applications deployed in the industry.
MEASURE FOR MEASURE
Geoff Royston
Look around your house. Is there a clock or other timepiece? A ruler or tape measure? What about some weighing scales? Three out of three? You may not be a metrologist, but you are clearly familiar with their subject matter and well equipped with some of their basic tools.
My piece for this issue of Impact has been prompted and informed by the recently published book Beyond Measure by James Vincent and also by The Tyranny of Metrics by Jerry Muller.
Beyond Measure takes the reader through a lively history of measurement from the ancient Egyptians monitoring the height of the floodwaters of the Nile, through mediaeval standards for weights and measures, on to the birth of the metric system during the French Revolution - and then to the present day where it seems that almost everything is being measured by everyone – or, more insidiously, surreptitiously, by someone.
THE SPREAD OF STANDARDISED MEASUREMENT The ability – and need – to measure time, distance, and mass underpins physical sciences and, arguably, civilisation. For instance, the societal importance of regulating such measurement was recognised in the Magna Carta of 1215, clause 35 of which reads: ‘There is to be one measure of wine throughout our kingdom, and one measure of ale, and one measure of corn, namely the quarter of London, and one breadth of dyed, russet and haberget cloths, that is, two ells* within the borders; and let weights be dealt with as with measures’. (* an ell was the length of King Henry I’s forearm!).
The societal importance of weights and measures regulations was further demonstrated by the intertwining of the French and the Metric revolutions, and continues to this day: Beyond Measure notes for example how arguments over use of metric rather than imperial measures - featuring slogans like ‘Rule Britannia - in Inches not Metres’ fostered the growth of UKIP and the Brexit movement.
Historically, searching for a reliable standard has involved striving for ever greater accuracy and precision. So standards have developed from the King’s forearm’s ell of the Magna Carta, to the platinum cylinder kilogram of the French metric revolution, to the modern standard for the second based on the frequency of electromagnetic waves from caesium-133 in an atomic clock.
Reference standards now exist for an astonishing range of things, far beyond fundamental physical units: amongst those mentioned in Beyond Measure are peanut butter, powdered radioactive human lung - and a standardised process for making tea. Similarly, the range of what is routinely measured has expanded hugely. Measurement of inputs, outputs and performance has become ubiquitous in the workplace. Lately, with credit ratings, body mass indices, daily step counts and so on, we have seen the emergence of what has been termed the ‘quantified self’.
MEASUREMENT: GOOD OR BAD? Positions on the merits of this spread of measurement and quantification vary. The eminent Victorian physicist William Thomson, Lord Kelvin, was in no doubt: ‘When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind’.
A more nuanced view is given by the management writer Charles Handy In his book The Empty Raincoat: ‘The first step is to measure whatever can easily be measured. This is OK as far as it goes. The second step is to disregard that which can't be easily measured or to give it an arbitrary quantitative value. This is artificial and misleading. The third step is to presume that what can't be measured easily really isn't important. This is blindness. The fourth step is to say that what can't be easily measured really doesn't exist. This is suicide’.
Such criticisms relate to a modern unease that measurement may have gone too far, with a view that excessive quantification discounts the more ‘human’, qualitative, elements of life. In fact, such unease is far from new, as shown in the words of the Greek philosopher Plutarch: ‘The measure of a man's life is the well spending of it, and not the length’, or of Oscar Wilde ‘s criticism about a person who ‘knows the price of everything and the value of nothing’. In Beyond Measure James Vincent comments that measurement can conflict with ‘something deeper and unquantifiable in ourselves’, echoing Keats’ ‘unweaving the rainbow’ – seeing the rationalisation of nature as removing its magic and meaning. (For him, clearly, but for others, understanding the workings of the natural
world enhances rather than diminishes their appreciation; see for example Richard Dawkins’ book Unweaving the Rainbow: Science, Delusion and the Appetite for Wonder.)
This is beginning to take us beyond the scope of this article so, without ignoring criticisms of measurement, let’s focus mainly on measurement in management.
MEASURING THE THING RIGHT AND MEASURING THE RIGHT THING For measurement in ‘softer’ areas – including management – issues beyond reliability, accuracy and precision become more challenging – not least validity. Does the measurement correspond to what it is meant to be measuring? And how far is it measuring the right thing anyway? So, for example, how well (if at all) does a particular measure for organisational performance correspond to the success of an enterprise? As one of the key figures in the post-war growth of Operational Research, Russ Ackoff, said: ‘Managers who don't know how to measure what they want settle for wanting what they can measure’.
Beyond Measure and The Tyranny of Metrics present numerous instances of what they describe as ‘excessive and inappropriate measurement’, ranging from over-extended applications of Frederick Taylor’s ‘time and motion’ studies in the early 1900s to the infamous example of the Vietnam War’s reliance on ‘body count’.
These books note how problems grow, with unintended consequences such as gaming the system, when measurement is used to penalise poor performance. They relate that when the NHS penalized hospitals with A&E wait times longer than four hours, some hospitals responded by delaying the handover of patients from arriving ambulances, thus keeping the wait within the hospital down - but seriously reducing the ability of the ambulance service to meet its response time targets. Or when surgeons ‘cream’ the easier cases, hesitating to take on the riskier procedures for which the success rate, and so their apparent performance, will inevitably be poor. Such behaviour exemplifies Goodhart’s Law: ‘Any measure used for control is unreliable’.
Such hazards need to be recognised, but not overemphasised. As Muller, in The Tyranny of Metrics, notes: ‘The problem is not measurement, but excessive measurement and inappropriate measurement—not metrics, but metric fixation’.
MEASURED JUDGEMENT One way of avoiding ‘metric fixation’ is to favour ‘subjective judgment’ over ‘objective measurement’. But although there will be some situations in which relying on a manager’s personal experience and instincts is appropriate, and others where this approach will be inferior to one grounded on data and analysis, decisions often benefit from deploying both experience-based judgement and data-based measurement. A good example can be found in The Signal and The Noise by Nate Silver in his revisiting of the story of Moneyball. That book – and resulting film – was about how analytics had transformed the process of recruiting baseball players from one relying on the observations and intuitions of traditional scouts to one where analysis of the huge database of baseball performance statistics was successfully used to identify promising players that scouts were missing. Nate Silver points out that at first this seemed to threaten the jobs of baseball scouts but in the years that followed teams that that had leant heavily on statistical analysis added in more scouting to the mix, while teams that had relied strongly on scouts added in more analytics. The best results were produced by a judicious blend of the two approaches.
Which leads me to end this piece with the (somewhat surprising given the book’s title) concluding words of The Tyranny of Metrics, ‘Ultimately, the issue is not one of metrics versus judgment, but metrics as informing judgment, which includes knowing how much weight to give to metrics, recognizing their characteristic distortions, and appreciating what can’t be measured’.
© Faber
Dr Geoff Royston is a former president of the OR Society and a former chair of the UK Government Operational Research Service. He was head of strategic analysis and operational research in the Department of Health for England, where for almost two decades he was the professional lead for a large group of health analysts.
© Princeton University Press
