What are the efficient ways to light up our roads or travel during the night with minimal cost, without impacting safety?

Combining multiple innovation together to make it simple. When we cannot put carpet on entire earth, we wear sandals or shoes isn't it. Then why can't we do the same when we want to go in the night. Instead of lighting up the entire place, why don't we carry a small torch light with us. (similar to how coal mine workers work, having an headlight on the head)

(Step 0) Early to sun and early to bed - follow the sun to avoid the need to use artificial light. You will see very few people after 6pm in the evening.
Today people go to sleep very late and wake very late - If we make mandatory laws to start offices, shops, schools and all other institutions by 7.30 Am and close all of them before 16.30 pm. (Unless they are running 247 operations ins shifts.) This will make people wake up early and ensure that they sleep early.*
Benefits
(a) Good for mind, body and soul - sync with the nature
(b) Improves health, as people will not eat food late night and have their dinner close to sunset. (which is the best time)
(b) Improves work life balance - Automatically takes care of labour laws
(c) Improves your thinking and ability to do better work early in the morning
(d) Reduces laziness among citizens
(e) No pollution when trees start to emit carbon di oxide.
(f) Improves productivity by 10-20%
(g) Family members get time to spend with their children, when they are back from school
(h) School children get time to play in the day time, after school hours.
(i) Reduces probability of alcohol intake and unnecessary spend by the people on alcohol and night out parties
(g) Improves savings as the cost to manage shop is reduced and citizens pay lesser taxes as the 30% of the lighting costs get reduced which is paid from the taxes of people.
If we cannot follow it fully - we need then follow the below steps.

We understand that in a dynamic world, we will have need to travel and work after sunsets - for that we can follow these simple procedures

( step 1) SmartCap (when you are not in a vehicle), with good headlight along with a sensor-rigged water proof helmet, continually monitors and guides you when you plug in the headset into your ears.
All vehicles today have decent headlight :)

(Step 2) Have retro-reflectors on both side of the roads, which will help you to navigate very easily on highways. (Less cost - long life - No maintenance - no health impact - environment safe)
Retroreflectors are devices that operate by returning light back to the light source along the same light direction.

Tritium lighting is not considered as exposure to tritium, even at low doses, which can lead to adverse health effects such as an increased risk of mutation and cancer.

Still better - have trees which will illuminate on their own. Fireflies are able to emit light via a chemical reaction in which luciferin is converted to oxyluciferin by the luciferase enzyme. Some of the energy released by this reaction is in the form of light. The reaction is highly efficient, meaning nearly all the energy put into the reaction is rapidly converted to light.
https://www.dailymail.co.uk/sciencetech/article-5178531/MIT-creates-bioluminescent-trees-glow-like-fireflies.html

(step 3) Mandatory law to have reflective tapes on your vehicles and also to have a reflective coat when you are going in the dark.

(Step 4) Promote travelling using public transport (24*7) from one place to another like trains, buses, auto and cabs which will help in generating employment and brings down the cost of public transportation and reduces the need to maintain vehicle.

(Step 5) Deploy self illuminating roads in major cities,w here we expect people to work 24*7 ( Refer the same in the below solution)

Done - You have the solution to avoid maximum street lights on highways at least in very simple and easy ways.

In one Chinese city, costly streetlights could soon be a thing of the past. By 2020, the Tian Fu New Area Science Society plans to launch an artificial moon to light up the night sky. If the plan goes through, the so-called “illumination satellite” would orbit above the Chinese city of Chengdu and glow in conjunction with the actual moon, but shine eight times brighter. The organization says it will launch three more satellites in 2022 — potentially replacing streetlights in urban areas. The plans were announced by Wu Chunfeng, head of the society, at an innovation conference in Chengdu on October 10.

Despite shining light in a similar way, the satellite boasts one advantage that the moon doesn’t — human control. Chunfeng says that both the location and brightness of the human-made moon can be changed, and that it can be completely shut off if necessary. And since the satellite is mobile, it can assist in disaster relief by beaming light on areas that lost power.
Cutting Costs
The lunar project aims to cut down on costly streetlights in China’s bustling cities. By lighting up just 31 square miles (50 square kilometers) of Chengdu’s night sky, the mini-moon could save the city an estimated 1.2 billion yuan ($174 million) each year.

The three follow-up moons, though, will be able to cover much more ground. The trio will take turns, based on who’s facing the Sun, beaming light on the city streets. Working together, they’ll be able to illuminate 2,000 to 4,000 square miles (3,600 to 6,400 square kilometers) for up to 24 hours.

Potential Pitfalls

(1) In the 1990s, an unsuccessful attempt was made by the Russian Federal Space Agency to launch similar reflective orbiters. After one of their satellites failed during deployment, they ended up scrapping the project.

(2) Impact on the sleep patterns of humans and animals, will interfere in the natural ecosystem and will lead to potential side effects.

(3) Dependent on few people to get the lighting done - failure for even one day can cause a huge impact on living of the people

(4) Needs alternative when the satellite fails - so the costs will be the same.

(5) High cost to launch

A team of scientists at Michoacan University in Mexico have created a type of cement that glows in the dark. Roads made with this material would be able to light up highways and bike paths without the use of electricity, purely by absorbing energy from the sun’s rays. Similarly, buildings and other structures constructed with this concrete coating would be illuminated as well.

Phosphorescent materials absorb energy from radiation such as the ultraviolet light emitted by the sun—or by lamps, if indoors—energy they later emit as light, which can be seen after dark. As it loads up energetically with ultraviolet rays, even on cloudy days the cement will be able to absorb enough energy to glow during dark periods for up to 12 hours.

This newly-developed concrete isn’t ready for the marketplace yet and it will need to be further studied to understand the material’s new properties. For example, its inorganic nature may pose new questions about the stability of its compounds and how to perform repairs. These self-lit roads, could be particularly beneficial in areas with limited access to electricity, Carmen Andrade, a researcher at the Spanish National Research Council Institute of Building Sciences in Madrid, told Scientific American.

The announcement of luminous concrete comes on the heels of the recently published atlas on light pollution, which reveals that a third of humanity can no longer see the Milky Way. It’s possible that these roads could one day replace street lights, potentially reducing this light pollution. But, depending on their luminance, they could alternately add to the mass of artificial light that obscures the stars.