Gas works which are expected to take 14 weeks to complete are likely to cause traffic disruption, with temporary traffic lights in place.
The essential works in Knebworth's Stevenage Road began on January 9.
Gas network Cadent explained: "We're laying new pipes for a greener gas future.
"Your gas supply will not be affected.
"We will be working in the area between 30 Stevenage Road and the railway bridge.
"Temporary traffic lights will be used to facilitate our works safely and efficiently and will be under manual control during peak hours.
"If you have any questions, you can call us on 0800 151 2404 or email CustomerCareEastern@cadentgas.com. Our team are available Monday to Friday 8am to 8pm, and Saturday 9am to 4pm."
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