Maximizing collection efficiencies is imperative for the reduction of overall solid waste management costs.

By Daniel P. Duffy

Collection costs account for 50% to 70% of a solid waste budget. In the past, collection routes were intuitively drawn by humans using highlighters or pens to draw on road maps. While frequently sufficient (humans can often correctly arrive at intuitive answers to complex questions), this process could never optimize the use of a waste collection fleet. That requires the high speed and accuracy of a computer mated with software specifically designed to lay out the most efficient collection routes possible.

Waste Collection Options
There are basically three options for organizing waste collection and pickup depending on whether the municipality or the individual is responsible for ensuring that waste is picked up, and whether the municipality or a private company does the actual collection.

In the first option, the local municipality provides refuse collection and pickup to households and businesses directly. In this instance a department of the municipality oversees the collection service. Fees are determined by city ordinance or directly by the voters. More often than not, the waste collected directly by a municipality is disposed of in a landfill owned and operated by the municipality or some other governmental agency like the county. The primary advantage of this approach is the complete control given to the municipality over the entire process. Prices can be controlled directly, while safety and environmental standards are met by the community most at risk from environmental failures. The main disadvantage is the lack of competitive pressures leading to price reductions and innovation.

In the second option, municipalities contract with private refuse haulers who provide refuse collection services. The municipalities sign these contracts on behalf of their residents and businesses. The private companies collect waste from individual households and businesses under contract with the municipality in which these households and businesses are located. The collected waste can be disposed of either in the private hauler’s own landfill or, occasionally, the waste can be shipped to a landfill owned by the municipality.

In the last option, individual households and businesses directly contract with private refuse haulers for residential refuse collection services without the municipal middle man. Individual customers are billed directly by the waste haulers without the municipality being involved. The obvious advantage is that (at least in theory) competition is maximized and the cost of collection can be minimized. This is said to be in theory because there are structural limitations preventing maximum efficiencies in the presence of competition between haulers concerning staked-out collection areas. The fact is, hauling efficiencies are maximized by uniform hauling routes where there are no gaps in coverage or discontinuities in the routes. Though not exactly like a utility with a fixed infrastructure (roads, sewers, or water mains), waste hauling has many structural similarities. It simply doesn’t make economic sense for a company to send a hauling truck out to a region where only a few widely separated customers exist. Haulers may be happy to provide the service, but the costs will be such that the potential isolated customers may not experience the full price savings that would theoretically result from competition. So in a classical economics situation of pure competition (where multiple haulers are competing at roughly equal market shares in the same hauling route markets) the structural costs—and the price for collection services—may actually increase.

Transfer stations can be used by any of the above collection options. Transfer stations regionalize waste hauling by allowing waste collection trucks from widely separated and remote areas to funnel their efforts toward a single point where the waste can be transferred to a larger hauling truck for long distance transport to the landfill. Though the larger truck may cost more to operate than the smaller collection trucks in terms of cost per truck mile, this is offset by the much greater capacity of the long-distance hauler, resulting in much lower transportation costs per ton of waste collected. Cost per ton is the only metric used to measure waste management company operating costs. The factors used to determine the cost of waste transfer operations include the effective load capacity of each hauling truck, the cost to operate the transfer facility (prorated per ton of waste received at the transfer station), the distance from the transfer station to the landfill, and the capital costs of the transfer facility construction (amortized over the operating lifetime of the facility and further prorated per ton of waste received each amortized year). The direct cost per ton to transport waste from a transfer station to final disposal at the landfill is determined as follows:

Transportation cost per ton = (trailer cost / hour) x (number of hours) x (tons per load)

The total cost (including station operation, amortized construction costs, and landfill disposal costs) of hauling waste from a transfer station to the landfill is calculated below:

Total transfer cost per ton = construction and operation costs + transportation cost + disposal cost

Economics
Time is money, especially when picking up refuse and transporting it to a landfill for disposal. Key to this evaluation is the time it takes for solid waste collection, as determined by the following formula:

Y = a + b + (c x d) + e + f

Where:

Y = the total collection time for an individual truck to complete its collection route(s) and deposit waste in the landfill

a = the travel time from the truck’s service garage to its collection route starting point

b = the time spent on its route collecting waste from individual pickup points until the truck is full and/or its route is completed

c = the number of trips a collection truck will take to the landfill, which can equal 1 if the amount of waste collected on the route is equal to the truck’s hauling capacity, or more than one if either the amount of waste on the route exceeds the truck’s capacity or the truck is working more than one collection route per workday

d = the time to drive a fully loaded truck to disposal facility, get the truck weighed and ticketed as it enters the facility, unload the waste at the landfill’s working face, and return to the collection area

e = the time to drive to the truck’s service garage at the end of the trip or the end of the workday

f = off-route time, such as time spent on refueling, lunch, and other breaks for the driver and loaders, usually a standard fraction of the total collection time

Each truck’s hauling route will be somewhat different, even if certain elements of the overall cycle are the same. The total number of vehicles required in a waste-hauling fleet is a function of the number of customers and the frequency of collection per workday each workweek as determined by the following formula:

N = (S x F) / (X x W)

Where:

N = the number of operating vehicles required for the fleet, with the actual number being higher to account for that part of the fleet that is in for planned maintenance or repair work

S = the total number of customers served per week as defined by the numbers of pickups where a customer can be either an individual residential curbside pickup or a large dumpster serving a commercial or office building

F = the collection frequency, which is usually equal to once per week for residential customers but can be twice a week or more for large commercial and office customers

X = the number of customers a truck can serve daily, determined by the length of a workday or an operating shift divided by the total collection time for a truck route (determined above)

W = the number of workdays or operating shifts per week, with large-hauling operations that serve major communities performing more than one shift per workday

The key factor in minimizing the amount of time (and money) necessary to collect and haul waste is “b”, the time spent on its route collecting waste from individual pickup points until the truck is full and/or its route is completed. This reduces the number of route cycles per truck and the number of trucks required by the hauling fleet by maximizing the number of customers a truck could service each workday. All other factors are a function of fixed distances (such as the time from the garage to the start of the collection route) or fixed periods (such as the number of hours in a workday or shift) and cannot be significantly modified. However, the actual time spent collecting waste can be changed by changing collection routes and driving directions to maximize efficient collection. This is where the software for collection and routing comes in.

Functions and Goals
No mechanism or operation will ever be 100% efficient. The function of collection and routing software is to get waste collection and hauling efficiencies as close to perfect as possible.

Collection and routing software searches out the most efficient routes possible, laying out those routes that avoid deadheading and backtracking. Deadheading is defined as the time when the vehicle is moving but is not in service. This results in the collection truck having to backtrack along a street that has already been serviced to get to another part of the service network. Simply put, any truck movement that is not directly moving to a new collection point is wasted movement resulting in unnecessary cost.

A good collection and routing software program will help a truck fleet manager accomplish the following:

• Decrease labor, fuel, and tire costs
• Decrease unnecessary mileage and overtime
• Ensure that customer service is provided in a timely fashion
• Ensure quality control and crew accountability
• Allow accurate pricing of services while maintaining required profit margins
• Add new customers and expand routes without disrupting schedules or reducing efficiency leading to faster business expansion
• Balance routes to level workloads among the various trucks in the fleet

Implementing these software programs often requires manual effort up front. City workers and volunteers are hired to follow behind collection trucks recording each and every pickup address and location in detail and later entering this data into the department’s database. Database implementation can take more than three months to accomplish and troubleshoot, but it is time well spent, paying significant dividends in the long run.

Armed with this database and a computerized map of the municipality’s streets and roads, the collection and routing software automatically plots collection stops and route information to computerized street maps based on the address location of each customer. Most software systems build on this original database by graphing collection stop information, mileage, and transit times for each route.

Critical to the effective use of collection and routing software is an effective Geographical Information System. Most collection and routing software packages are fully integrated with existing GIS systems on the market. The main goals of the integrated GIS and routing software is to balance collection routes so that one truck does not have a much longer and larger route than another truck, minimize the time spent on each route collecting waste, and (if possible) eliminate collection routes by merging entire routes or parts of routes into other routes.

GPS Tracking
Often working hand in hand with waste collection and routing GIS software programs use Global Positioning System (GPS) technology to track vehicles. With the GPS, the truck fleet manager can ascertain the precise location of his trucks at regular intervals.

GPS tracking systems come in two types, passive and active. Passive systems download data for retrieval later. Active systems report vehicle movements back to the main office in real time. The system that sends data back to the central office via radio transmittal is preferred to a system that records locations for download into a data base later, since broadcasting provides real time information of the truck’s whereabouts and efficient use. Broadcast can be by cellular phone, radio, or satellite linkup. The truck’s location is easily displayed on the GIS interface of the collection and routing software display.

GPS units have long been used by the shipping industry to track cargo, but have only been recently used to track truck operations and movements.

Given that waste collection trucks normally operate on clear streets and roads without overhead obstruction, the need for an antenna that is not a direct line of sight is usually not an issue. Often, GPS modules double as voice and data communication systems. In private applications, GPS modules are used for theft protection and vehicle recovery. This is rarely a problem for waste trucks. However, the GPS will show the fleet manager that his tucks are following their appointed routes and meeting deadlines.

Should something prevent the driver from doing so, a description why can be relayed instantly back to the dispatcher.                      MSW

Daniel P. Duffy, PE, is an environmental engineer employed by URS Corp. in Akron, OH.

MSW - September/October 2006