Exercises: Transport and sustainability

Order from lowest to highest environmental impact per person on an urban journey and justify the order: single-occupancy car, bus, bicycle and underground.

Explain what sustainable mobility is and mention three specific actions a city can take to promote it.

The graph compares CO₂ emissions per passenger per kilometre for various modes of transport. Calculate the emissions for travelling to school and back ($15\ \text{km}$ in total) by car and by bus, and state how many times more one option emits compared to the other.

Rank these transport energy sources from lowest to highest emissions when driving/moving and justify the order: petrol, electricity from renewable sources, diesel and human power (bicycle).

Explain what a "protected cycle lane" is and why it increases bicycle use much more than a simple line painted on the road.

What is an "intermodal" journey? Describe a realistic example of a journey to school combining cycling, taking the train and walking, and what is needed to make that combination convenient.

Name three non-environmental benefits of walking or cycling to school (health, financial savings, independence) and explain them in one sentence.

Explain what a shared vehicle service (pay-per-minute car or scooter hire) is and reason in which cases it can reduce the total number of cars in a city.

A local council wants to reduce traffic in the city centre. Analyse these four measures — cycle lane, pedestrianisation, park-and-ride car park on the outskirts, and shuttle bus — and order them by speed of implementation and expected impact, justifying your criteria.

Electric cars do not emit tailpipe gases while driving, but does that mean they are "zero emission"? Reason your answer using the life cycle approach: battery manufacturing and the source of electricity.

Twenty students who travel $4\ \text{km}$ a day by car to get to school decide to switch to cycling. With these figures per passenger: $120\ \text{g}$ of CO₂ per kilometre by car versus $0\ \text{g}$ by bike, calculate how many kilograms of CO₂ are avoided in a month of 20 school days.

A city bus consumes the equivalent of 8 litres of diesel per $100\ \text{km}$ and carries an average of 20 passengers; a car uses 6 litres per $100\ \text{km}$ with a single occupant. Calculate the consumption per passenger per $100\ \text{km}$ in both cases and comment on the result.

A city pedestrianises its centre and local businesses fear losing customers. Analyse what usually happens to sales when footfall increases (more foot traffic, more local shopping) and what supporting measures you would put in place during the transition.

Explain what "last-mile logistics" is and describe two ways to make it more sustainable (shared pickup points, cargo bikes, electric vans), highlighting their advantages.

A family makes two daily journeys of $10\ \text{km}$ by car for 220 days a year. Taking $120\ \text{g}$ of CO₂ per kilometre by car and $70\ \text{g}$ by bus, calculate current annual emissions and how much they would be reduced by if half of the journeys were made by bus.

Compare an electric scooter and a bicycle for urban journeys of $3\ \text{km}$: energy consumed, physical exercise, safety, and performance in rain or cold weather. Defend one option while acknowledging the strengths of the other.

A mobility audit at your secondary school (600 students) reveals that 45 % arrive by private car (with an average occupancy of 1,1 students/vehicle), 30 % by bus, and 25 % on foot or by bicycle, causing severe traffic jams and hazardous situations at the gate at 8:00.

1. a) Design a school mobility plan with three specific technical or organisational measures aimed at reducing car trips by at least half within one school year.
2. b) Define two verifiable quantitative indicators (specifying their calculation formula and unit of measurement) for the school management to evaluate the plan's effectiveness on a monthly basis.
3. c) Justify a low-cost physical intervention on the public street in front of the school (tactical urbanism) that increases the safety of students who commute actively.

The construction of a 400 km high-speed railway line has generated a carbon footprint of 1,5 million tonnes of CO₂ equivalent due to earthworks, tunnels, and concrete work on viaducts. In that corridor, travelling by plane emits 120 g of CO₂ per passenger·km, while the train emits 24 g of CO₂ per passenger·km with the current electricity mix.

1. a) Calculate how many full passenger trips by train (replacing the plane) are needed to offset the initial impact of the infrastructure.
2. b) If the line carries 3 million passengers per year and 70 % of them shift from flying, predict in how many years the environmental payback of the project will be achieved.
3. c) Justify how this payback period would change if the country's electricity mix shifted from 50 % to 90 % renewable generation.

A 1300 kg passenger car consumes 5,5 L of petrol per 100 km when only the driver travels. Each additional 75 kg passenger increases the vehicle's consumption by approximately 0,1 L per 100 km (data: burning 1 L of petrol emits 2,3 kg of CO₂).

1. a) Quantitatively refute the statement 'carpooling pollutes the same as driving alone, it is just shared', calculating and comparing emissions in grams of CO₂ per passenger·km when only the driver travels versus when 4 people travel together.
2. b) If carpooling is promoted in an industrial estate with 1200 workers and average occupancy rises from 1,1 to 2,2 people per vehicle, predict how many fewer cars will circulate and how many square metres of parking space will be freed up (estimate 12 m² per space).
3. c) Justify why reducing the number of vehicles by 10 % during peak hours can reduce time lost in traffic jams by more than 30 %.

A school 'bike bus' route is to be set up to arrive at the educational centre by 8:20 with the following technical conditions:

• Total route length: 3,6 km on shared urban roadway.

• Intermediate stops: Stop 1 (km 0,9), Stop 2 (km 1,8), and Stop 3 (km 2,7).

• Average convoy pedalling speed: 12 km/h.

• The route crosses a problematic two-lane roundabout without traffic lights at km 2,2.

1. a) Design the technical timetable for the route by calculating the exact departure and passing times for each stop, adding 2 minutes of technical dwell time at each point for students to join, and arriving 10 minutes early at the school.
2. b) Propose an operational protocol and technical traffic-calming measures to safely cross the roundabout at km 2,2, ensuring priority for the bicycle convoy.
3. c) Define two quantitative indicators to evaluate the impact of the bike bus after six months of operation.

A company with 200 employees adopts a model of 3 teleworking days per week. Annually, its environmental audit records the following average data:

• 4500 km per year are avoided per employee in a diesel car (consumption: 5,8 L/100 km; 2,6 kg CO₂/L).

• 20 % of the workforce has moved their residence to municipalities located 60 km away, doubling the travel distance during their two on-site days compared to their previous situation.

• Electricity and heating consumption in homes has increased on average by 1,8 kWh per teleworker and teleworked day (emission factor: 0,22 kg CO₂/kWh).

1. a) Interpret these data and predict whether teleworking alone guarantees a net reduction in emissions or if a "rebound effect" may appear that cancels out the benefit.
2. b) Make a numerical estimate of the net annual emissions balance (CO₂ avoided in transport versus additional CO₂ from domestic consumption and distant commutes).
3. c) Design two mobility management guidelines that the company should implement so that teleworking genuinely reduces its corporate ecological footprint.

A city of 200 000 inhabitants must connect its city centre with a new hospital 6 km away. The forecast demand at peak hour is 2600 passengers/hour per direction. The city council is evaluating two alternatives:

• Option A (Tramway on dedicated right-of-way): Infrastructure cost of 14 million €/km; units for 220 passengers; maximum frequency of 5 minutes; system service life of 35 years.

• Option B (Bus Rapid Transit line, BRT): Road adaptation cost of 1,5 million €/km; articulated vehicles for 95 passengers; maximum frequency of 2 minutes; vehicle service life of 12 years (with battery replacement at 6 years).

1. a) Check by means of hourly capacity calculations whether both options can absorb the forecast peak demand.
2. b) Compare the resilience and flexibility of both systems in the face of track/road incidents (unexpected roadworks, convoy breakdown, or demonstrations).
3. c) Reasonably argue which of the two options offers a more favourable long-term cost-benefit balance taking into account the city's density and size.

An electoral proposal promises to replace 100 % of a city's 150 000 combustion passenger cars with electric cars in 8 years, keeping the road network and the total number of vehicles in circulation unchanged.

1. a) Critically analyse which urban problems this measure solves and to what extent it improves local air quality and acoustic comfort.
2. b) Technically refute why this measure does not solve the problem of traffic congestion, accident rates, public space occupancy (knowing that a car remains parked for 95 % of its useful life occupying about 12 m²), or PM10 and PM2,5 particulate pollution arising from tyre and brake wear in vehicles that weigh between 15 % and 25 % more due to the battery.
3. c) Design an alternative proposal to redistribute the cross-section of a 20-metre-wide urban avenue (currently 4 car lanes and 2 parking lanes) prioritising modal efficiency and environmental sustainability.

A secondary school with 800 students obtained the following percentages in its transport survey:

• Mode A (Active mobility: on foot, bicycle, or non-motorised scooter): 30 %

• Mode B (Public transport: school bus or city bus): 40 %

• Mode C (Carpooling with 2 or more students): 10 %

• Mode D (Individual private car with 1 student): 20 %

1. a) Design a mathematical formula to obtain a "Mobility Sustainability Index" ($I_{SM}$) that scores from 0 to 100. Assign a weighting coefficient between 0 and 1 ($P_A, P_B, P_C, P_D$) to each mode, justifying the chosen values based on their energy efficiency and public road occupancy.
2. b) Calculate the current value of the school's $I_{SM}$ with your formula.
3. c) If the school installs lockers and covered bike racks, managing to get half of the students who came by individual car (Mode D) to switch to active mobility (Mode A), calculate the new index and predict how many cars per day will stop congesting the school entrance.