How DART Plans its Fleet to Best Serve Central Iowa

Providing public transit service to Greater Des Moines residents depends on more than smart planning and a reliable team of bus operators: It rides on the more than 140 buses in our fleet – literally. 

By the numbers, DART has:  

• 105 30-foot and 40-foot fixed route buses, and 

• 40 smaller buses for paratransit and on demand services 

Most years, we buy five to ten new buses to replace aging vehicles in our fleet. Although new buses are expensive, replacing old ones rather than paying for their upkeep is most cost-effective. Annual maintenance costs for buses past their useful life range from $35,000 to $65,000 higher than average. 

The majority of funding for new buses comes from the federal government and is paid for through DART’s capital budget. Only a small portion of the total cost comes from local property tax dollars, allowing us to use local dollars primarily for our daily operating expenses. 

To ensure the bus fleet meets our needs, we regularly evaluate our buses and explore new technologies to identify opportunities for even greater efficiency and cost-savings.  

Scroll down to discover answers to five of the most common questions we receive about our bus fleet.
 

1. How does DART determine what buses are needed for service?

We plan our fleet based on the types of service we offer and our expectations for peak demand. The buses we use on our fixed routes are selected with the busiest times of day in mind. 

“It’s important to choose buses that can accommodate many people at one time because ridership ebbs and flows throughout the day,” said Luis Montoya, DART’s Chief Planning and Operations Officer. “We need to be able to serve customers well at our busiest times, like the early morning commute and late afternoons when students leave school.” 

Even when a route is less busy, keeping a large bus on that route is more efficient, Montoya said. Swapping it out for a smaller vehicle during off-peak hours increases operating cost by requiring more back-and-forth trips to the bus garage without picking up customers and increases the total number of vehicles DART needs to maintain in its fleet. 

Right sizing the fleet to match peak demand is comparable to how our roads are designed. I-235 has multiple lanes so it can accommodate a high volume of cars during busy morning and afternoon commutes, but at other times, most lanes are wide open. 

2. Sometimes I see an empty bus driving down the road. Wouldn't it be cheaper to operate smaller vehicles, like the ones you use for DART On Demand and Paratransit?

While we provide an average of 12,000 rides on a typical weekday, ridership varies throughout the day and people get on and off at different points, meaning each bus won’t be full all the time.  

“Each time you pass a bus, it’s important to remember it is only a snapshot in time,” said Montoya. “A bus with fewer passengers may have just dropped a larger group off at a stop or it could be driving to or from our bus garage at the start or end of an operator’s work shift.” 

Using smaller vehicles wouldn’t necessarily be cheaper because DART’s highest cost for delivering service is actually the bus operator’s salary. Further, the cost of fuel, parts and maintenance for smaller buses is not much different than larger vehicles.  

On average, DART’s local bus routes serve an average of 17 passengers per hour per bus. The lowest ridership routes with more limited service carry about 10 passengers per hour and the highest-demand routes carry about 35 passengers per hour. Since 2019, we have piloted smaller 30-foot buses on our less busy fixed routes with more limited service. These are slightly cheaper than the large 40-foot buses most people see around town.  

Operating 30-foot buses comes with challenges, though. Each one has 23 seats (40-foot buses have 38) and only 17 when mobility devices are onboard because some seats have to be folded. In some cases, we’ve had to turn passengers away, causing riders to wait up to an hour for another bus. Some DART customers have also complained that riding on the 30-foot buses is rougher because they have a shorter wheelbase compared to larger buses.  

3. Is microtransit a better way to provide service?

Microtransit is a shared ride that operates when and where people request trips – a cross between a fixed route bus and a private rideshare service. Fixed route buses cost the same amount to operate regardless of how many passengers are onboard, while a higher volume of riders on microtransit can drive up the cost because more vehicles and bus operators are required to meet the demand. 

A small microtransit bus can serve an average of 3 to 5 people per hour, at a cost of $24 per trip. DART’s fixed route buses serve an average of 17 people per hour for about $6 per trip.  

4. What is DART doing to move to zero emissions or electric vehicles? 

We recently updated our Zero Emission Plan to inform how we build our facilities and plan our fleet for the future. That plan prioritizes making fleet decisions based on cost and funding availability, while preparing for the option of using alternative fuels or new technologies. 

Over the next several years, we expect diesel and unleaded buses to make up the bulk of our fleet as they remain the most cost-effective options. Biodiesel could be used to power our fleet, but doing so would require upgrades to our facilities. Compressed natural gas (CNG) is also popular and could reduce localized emissions, but the infrastructure and fuel prices are high. 

From 2021 to 2022, grant funding allowed DART to test battery electric buses on some fixed routes. However, it is unlikely that DART will purchase more electric buses in the next few years unless grant money becomes available. 

As we construct a new Operations and Maintenance Facility, we are preparing for future technologies within our fleet by increasing our power supply to support electric bus infrastructure and adding space to store new types of fuel – something our current facility is unable to accommodate. 
 

5. Have you considered using new technology like autonomous vehicles?

We regularly evaluate new technologies to see if they meet our fleet needs. By connecting with vendors and learning from other public transit agencies, we explore whether different types of vehicles would be more efficient and cost-effective.  

Autonomous vehicles (AV) – driverless or self-driving electric vehicles capable of sensing their environment with little or no human input – have drawn interest in recent years. Onboard technology ensures the vehicles will observe all traffic signals and respond appropriately to traffic and pedestrians. In some cases, AVs have an attendant onboard to assist passengers, but others do not have any transit staff members. 

Several transit agencies, like Contra Costa Transit Authority (CCTA) in California and Jacksonville Transit Authority (JTAFLA) in Florida, are piloting autonomous vehicle shuttles on short routes. Although using AVs could reduce operational costs if drivers aren’t required, the up-front cost for building the infrastructure within the transit agency and on city streets can be high. Most vendors rent their vehicles, which can also lead to higher costs to run a fleet over time.
 

PHOTO: Autonomous vehicle in testing in Jacksonville, Florida, courtesy of Jacksonville Transit Authority.

DART looks forward to exploring new technology and types of vehicles as more transit agencies report safety and efficiency data from their pilots and funding becomes available.  

Reimagine DART

As we redesign our transit network, planning our fleet to efficiently and effectively operate the new routes and services will be important. We also look forward to keeping a pulse on innovative ways to deliver our service, while ensuring we prioritize options that maximize the funding we receive. 

Learn more about Reimagine DART.