Formal pairs suit Writing Task 2. Neutral ones work anywhere. Informal ones belong in Speaking.
1.ease traffic congestion
formalreduce the number of vehicles blocking the roads
A congestion charge helped to ease traffic congestion in central London.
Reduce and relieve also collocate with congestion.
2.rush hour
neutralthe times of day when most people travel to or from work
Buses are packed during rush hour.
No article: during rush hour, in rush hour.
3.an efficient public transport network
neutrala system of buses and trains that works well
An efficient public transport network is the best way to reduce car use.
Public transport is British; public transportation is American.
4.the daily commute
neutralthe regular journey between home and work
For many Londoners, the daily commute takes over an hour each way.
Commute is also a verb: commute to work.
5.car ownership
formalthe fact or rate of people owning cars
Car ownership has risen sharply in China.
Levels of car ownership is a natural statistic phrase.
6.road safety
neutralthe prevention of road accidents
Lower speed limits near schools improve road safety.
Improve and promote collocate with it.
7.vehicle emissions
formalthe gases that cars and lorries release
Electric buses cut vehicle emissions in city centres.
Exhaust fumes is the more everyday phrase.
8.get stuck in a traffic jam
informalbe unable to move because of heavy traffic
I once got stuck in a traffic jam for three hours on the way to the airport.
Natural in Speaking. In Writing, use be delayed by congestion.
9.pedestrian zones
neutralareas of a town where cars are not allowed
Turning shopping streets into pedestrian zones made them safer and busier.
Pedestrianise is the verb (British spelling).
10.cycle lanes
neutralparts of a road reserved for bicycles
Separated cycle lanes encourage more people to cycle to work.
Bike lanes is more American.
11.go by bus
neutraltravel by bus
Most students go by bus because it is cheaper than the train.
No article after by: by bus, by train, by car.
Avoid: go by the bus → go by bus
12.take public transport
neutraluse buses, trains or trams to travel
If more people took public transport, cities would be quieter and cleaner.
Use public transport is equally correct.
13.transport infrastructure
formalroads, railways, bridges and stations
Poor transport infrastructure holds back economic growth in rural areas.
Invest in and upgrade collocate with it.
14.fuel prices
neutralthe cost of petrol and diesel
Rising fuel prices have pushed more people onto buses.
Prices rise, fall or soar.
15.get around
informaltravel from place to place in an area
The easiest way to get around my city is by metro.
A phrasal verb that is perfect for Speaking Part 1 and 2.