diff --git a/src/common/constants/TransportName.ts b/src/common/constants/TransportName.ts
index 8c49a76cee..29137c7f4c 100644
--- a/src/common/constants/TransportName.ts
+++ b/src/common/constants/TransportName.ts
@@ -1,8 +1,14 @@
-enum TransportName {
-  WebSocket = 'web_socket',
-  Comet = 'comet',
-  XhrStreaming = 'xhr_streaming',
-  XhrPolling = 'xhr_polling',
+export namespace TransportNames {
+  export const WebSocket = 'web_socket' as const;
+  export const Comet = 'comet' as const;
+  export const XhrStreaming = 'xhr_streaming' as const;
+  export const XhrPolling = 'xhr_polling' as const;
 }
 
+type TransportName =
+  | typeof TransportNames.WebSocket
+  | typeof TransportNames.Comet
+  | typeof TransportNames.XhrStreaming
+  | typeof TransportNames.XhrPolling;
+
 export default TransportName;
diff --git a/src/common/lib/transport/connectionmanager.ts b/src/common/lib/transport/connectionmanager.ts
index 53f4860ffc..cc6b1d6637 100644
--- a/src/common/lib/transport/connectionmanager.ts
+++ b/src/common/lib/transport/connectionmanager.ts
@@ -19,6 +19,7 @@ import { ErrCallback } from 'common/types/utils';
 import HttpStatusCodes from 'common/constants/HttpStatusCodes';
 import BaseRealtime from '../client/baserealtime';
 import { NormalisedClientOptions } from 'common/types/ClientOptions';
+import TransportName from 'common/constants/TransportName';
 
 let globalObject = typeof global !== 'undefined' ? global : typeof window !== 'undefined' ? window : self;
 
@@ -98,7 +99,7 @@ function decodeRecoveryKey(recoveryKey: NormalisedClientOptions['recover']): Rec
   }
 }
 
-const supportedTransports: Partial<Record<string, TransportCtor>> = {};
+const supportedTransports: Partial<Record<TransportName, TransportCtor>> = {};
 
 export class TransportParams {
   options: NormalisedClientOptions;
@@ -201,9 +202,9 @@ class ConnectionManager extends EventEmitter {
   connectionKey?: string;
   connectionStateTtl: number;
   maxIdleInterval: number | null;
-  transports: string[];
-  baseTransport: string;
-  upgradeTransports: string[];
+  transports: TransportName[];
+  baseTransport: TransportName;
+  upgradeTransports: TransportName[];
   transportPreference: string | null;
   httpHosts: string[];
   activeProtocol: null | Protocol;
@@ -481,7 +482,7 @@ class ConnectionManager extends EventEmitter {
    * @param candidate, the transport to try
    * @param callback
    */
-  tryATransport(transportParams: TransportParams, candidate: string, callback: Function): void {
+  tryATransport(transportParams: TransportParams, candidate: TransportName, callback: Function): void {
     Logger.logAction(Logger.LOG_MICRO, 'ConnectionManager.tryATransport()', 'trying ' + candidate);
 
     Transport.tryConnect(
@@ -1677,13 +1678,13 @@ class ConnectionManager extends EventEmitter {
     this.tryATransport(transportParams, this.baseTransport, hostAttemptCb);
   }
 
-  getUpgradePossibilities(): string[] {
+  getUpgradePossibilities(): TransportName[] {
     /* returns the subset of upgradeTransports to the right of the current
      * transport in upgradeTransports (if it's in there - if not, currentSerial
      * will be -1, so return upgradeTransports.slice(0) == upgradeTransports */
     const current = (this.activeProtocol as Protocol).getTransport().shortName;
     const currentSerial = Utils.arrIndexOf(this.upgradeTransports, current);
-    return this.upgradeTransports.slice(currentSerial + 1) as string[];
+    return this.upgradeTransports.slice(currentSerial + 1);
   }
 
   upgradeIfNeeded(transportParams: Record<string, any>): void {
@@ -1698,7 +1699,7 @@ class ConnectionManager extends EventEmitter {
       return;
     }
 
-    Utils.arrForEach(upgradePossibilities, (upgradeTransport: string) => {
+    Utils.arrForEach(upgradePossibilities, (upgradeTransport: TransportName) => {
       /* Note: the transport may mutate the params, so give each transport a fresh one */
       const upgradeTransportParams = this.createTransportParams(transportParams.host, 'upgrade');
       this.tryATransport(upgradeTransportParams, upgradeTransport, noop);
@@ -2101,7 +2102,7 @@ class ConnectionManager extends EventEmitter {
     this.proposedTransports.push(transport);
   }
 
-  getTransportPreference(): string {
+  getTransportPreference(): TransportName {
     return this.transportPreference || (haveWebStorage() && Platform.WebStorage?.get?.(transportPreferenceName));
   }
 
diff --git a/src/common/lib/transport/websockettransport.ts b/src/common/lib/transport/websockettransport.ts
index 90a93e2bc5..2324fc3021 100644
--- a/src/common/lib/transport/websockettransport.ts
+++ b/src/common/lib/transport/websockettransport.ts
@@ -8,9 +8,9 @@ import ErrorInfo from '../types/errorinfo';
 import NodeWebSocket from 'ws';
 import ConnectionManager, { TransportParams } from './connectionmanager';
 import Auth from '../client/auth';
-import TransportName from 'common/constants/TransportName';
+import { TransportNames } from 'common/constants/TransportName';
 
-const shortName = TransportName.WebSocket;
+const shortName = TransportNames.WebSocket;
 
 function isNodeWebSocket(ws: WebSocket | NodeWebSocket): ws is NodeWebSocket {
   return !!(ws as NodeWebSocket).on;
diff --git a/src/common/lib/util/utils.ts b/src/common/lib/util/utils.ts
index d3aca59d2f..a8bf3c4241 100644
--- a/src/common/lib/util/utils.ts
+++ b/src/common/lib/util/utils.ts
@@ -155,7 +155,7 @@ export function containsValue(ob: Record<string, unknown>, val: unknown): boolea
   return false;
 }
 
-export function intersect<T>(arr: Array<string>, ob: string[] | Record<string, T>): string[] {
+export function intersect<K extends string, T>(arr: Array<K>, ob: K[] | Partial<Record<K, T>>): K[] {
   return isArray(ob) ? arrIntersect(arr, ob) : arrIntersectOb(arr, ob);
 }
 
@@ -168,7 +168,7 @@ export function arrIntersect<T>(arr1: Array<T>, arr2: Array<T>): Array<T> {
   return result;
 }
 
-export function arrIntersectOb(arr: Array<string>, ob: Record<string, unknown>): string[] {
+export function arrIntersectOb<K extends string>(arr: Array<K>, ob: Partial<Record<K, unknown>>): K[] {
   const result = [];
   for (let i = 0; i < arr.length; i++) {
     const member = arr[i];
diff --git a/src/platform/nodejs/lib/transport/index.ts b/src/platform/nodejs/lib/transport/index.ts
index c5db7c0429..084b0cc955 100644
--- a/src/platform/nodejs/lib/transport/index.ts
+++ b/src/platform/nodejs/lib/transport/index.ts
@@ -1,7 +1,7 @@
-import TransportName from 'common/constants/TransportName';
+import { TransportNames } from 'common/constants/TransportName';
 import initialiseNodeCometTransport from './nodecomettransport';
 
 export default {
-  order: [TransportName.Comet],
-  implementations: { [TransportName.Comet]: initialiseNodeCometTransport },
+  order: [TransportNames.Comet],
+  implementations: { [TransportNames.Comet]: initialiseNodeCometTransport },
 };
diff --git a/src/platform/nodejs/lib/transport/nodecomettransport.js b/src/platform/nodejs/lib/transport/nodecomettransport.js
index f215c97a74..6e6655bb0d 100644
--- a/src/platform/nodejs/lib/transport/nodecomettransport.js
+++ b/src/platform/nodejs/lib/transport/nodecomettransport.js
@@ -10,11 +10,11 @@ import http from 'http';
 import https from 'https';
 import url from 'url';
 import util from 'util';
-import TransportName from '../../../../common/constants/TransportName';
+import { TransportNames } from '../../../../common/constants/TransportName';
 
 var NodeCometTransport = function (connectionManager) {
   var noop = function () {};
-  var shortName = TransportName.Comet;
+  var shortName = TransportNames.Comet;
 
   /*
    * A transport to use with nodejs
diff --git a/src/platform/nodejs/lib/util/defaults.ts b/src/platform/nodejs/lib/util/defaults.ts
index e6b55f18f8..8b29953cbd 100644
--- a/src/platform/nodejs/lib/util/defaults.ts
+++ b/src/platform/nodejs/lib/util/defaults.ts
@@ -1,14 +1,14 @@
 import IDefaults from '../../../../common/types/IDefaults';
-import TransportName from '../../../../common/constants/TransportName';
+import { TransportNames } from '../../../../common/constants/TransportName';
 
 const Defaults: IDefaults = {
   connectivityCheckUrl: 'https://internet-up.ably-realtime.com/is-the-internet-up.txt',
   /* Note: order matters here: the base transport is the leftmost one in the
    * intersection of baseTransportOrder and the transports clientOption that's supported. */
-  defaultTransports: [TransportName.WebSocket],
-  baseTransportOrder: [TransportName.Comet, TransportName.WebSocket],
-  transportPreferenceOrder: [TransportName.Comet, TransportName.WebSocket],
-  upgradeTransports: [TransportName.WebSocket],
+  defaultTransports: [TransportNames.WebSocket],
+  baseTransportOrder: [TransportNames.Comet, TransportNames.WebSocket],
+  transportPreferenceOrder: [TransportNames.Comet, TransportNames.WebSocket],
+  upgradeTransports: [TransportNames.WebSocket],
   restAgentOptions: { maxSockets: 40, keepAlive: true },
 };
 
diff --git a/src/platform/web/lib/transport/index.ts b/src/platform/web/lib/transport/index.ts
index 98674dd0e9..8fb1447186 100644
--- a/src/platform/web/lib/transport/index.ts
+++ b/src/platform/web/lib/transport/index.ts
@@ -1,11 +1,11 @@
-import TransportName from 'common/constants/TransportName';
+import { TransportNames } from 'common/constants/TransportName';
 import initialiseXHRPollingTransport from './xhrpollingtransport';
 import initialiseXHRStreamingTransport from './xhrstreamingtransport';
 
 export default {
-  order: [TransportName.XhrPolling, TransportName.XhrStreaming],
+  order: [TransportNames.XhrPolling, TransportNames.XhrStreaming],
   implementations: {
-    [TransportName.XhrPolling]: initialiseXHRPollingTransport,
-    [TransportName.XhrStreaming]: initialiseXHRStreamingTransport,
+    [TransportNames.XhrPolling]: initialiseXHRPollingTransport,
+    [TransportNames.XhrStreaming]: initialiseXHRStreamingTransport,
   },
 };
diff --git a/src/platform/web/lib/transport/xhrpollingtransport.ts b/src/platform/web/lib/transport/xhrpollingtransport.ts
index 5a7dfafd1c..c063397198 100644
--- a/src/platform/web/lib/transport/xhrpollingtransport.ts
+++ b/src/platform/web/lib/transport/xhrpollingtransport.ts
@@ -4,9 +4,9 @@ import XHRRequest from './xhrrequest';
 import ConnectionManager, { TransportParams } from 'common/lib/transport/connectionmanager';
 import Auth from 'common/lib/client/auth';
 import { RequestParams } from 'common/types/http';
-import TransportName from 'common/constants/TransportName';
+import { TransportNames } from 'common/constants/TransportName';
 
-var shortName = TransportName.XhrPolling;
+var shortName = TransportNames.XhrPolling;
 class XHRPollingTransport extends CometTransport {
   shortName = shortName;
   constructor(connectionManager: ConnectionManager, auth: Auth, params: TransportParams) {
diff --git a/src/platform/web/lib/transport/xhrstreamingtransport.ts b/src/platform/web/lib/transport/xhrstreamingtransport.ts
index 8640eec37e..57cf30e7b7 100644
--- a/src/platform/web/lib/transport/xhrstreamingtransport.ts
+++ b/src/platform/web/lib/transport/xhrstreamingtransport.ts
@@ -4,9 +4,9 @@ import XHRRequest from './xhrrequest';
 import ConnectionManager, { TransportParams } from 'common/lib/transport/connectionmanager';
 import Auth from 'common/lib/client/auth';
 import { RequestParams } from 'common/types/http';
-import TransportName from 'common/constants/TransportName';
+import { TransportNames } from 'common/constants/TransportName';
 
-const shortName = TransportName.XhrStreaming;
+const shortName = TransportNames.XhrStreaming;
 class XHRStreamingTransport extends CometTransport {
   shortName = shortName;
   constructor(connectionManager: ConnectionManager, auth: Auth, params: TransportParams) {
diff --git a/src/platform/web/lib/util/defaults.ts b/src/platform/web/lib/util/defaults.ts
index b182008c18..3dbd549733 100644
--- a/src/platform/web/lib/util/defaults.ts
+++ b/src/platform/web/lib/util/defaults.ts
@@ -1,15 +1,15 @@
 import IDefaults from 'common/types/IDefaults';
-import TransportName from 'common/constants/TransportName';
+import { TransportNames } from 'common/constants/TransportName';
 
 const Defaults: IDefaults = {
   connectivityCheckUrl: 'https://internet-up.ably-realtime.com/is-the-internet-up.txt',
   /* Order matters here: the base transport is the leftmost one in the
    * intersection of baseTransportOrder and the transports clientOption that's
    * supported. */
-  defaultTransports: [TransportName.XhrPolling, TransportName.XhrStreaming, TransportName.WebSocket],
-  baseTransportOrder: [TransportName.XhrPolling, TransportName.XhrStreaming, TransportName.WebSocket],
-  transportPreferenceOrder: [TransportName.XhrPolling, TransportName.XhrStreaming, TransportName.WebSocket],
-  upgradeTransports: [TransportName.XhrStreaming, TransportName.WebSocket],
+  defaultTransports: [TransportNames.XhrPolling, TransportNames.XhrStreaming, TransportNames.WebSocket],
+  baseTransportOrder: [TransportNames.XhrPolling, TransportNames.XhrStreaming, TransportNames.WebSocket],
+  transportPreferenceOrder: [TransportNames.XhrPolling, TransportNames.XhrStreaming, TransportNames.WebSocket],
+  upgradeTransports: [TransportNames.XhrStreaming, TransportNames.WebSocket],
 };
 
 export default Defaults;